Name: sample preparation for mass-spectrometry-based proteomics analysis of ocular microvessels
Uploaded: 2019-02-22T14:30:00
Description: Watch this Scientific Journal Video about Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels at JoVE.com

Dr. Manicam is supported by the Internal University Research Funding (Stufe 1) from the University Medical Centre of the Johannes Gutenberg University Mainz and a grant from the Deutsche Forschungsgemeinschaft (MA 8006/1-1).

All experimental procedures using animal samples were performed in strict adherence to the Association for Research in Vision and Ophthalmology (ARVO) Statement for the Use of Animals in Ophthalmic and Vision Research and by institutional guidelines. This study was conducted and approved at the Department of Ophthalmology, University Medical Centre Mainz.
NOTE: Porcine eyes together with optic nerve and extraocular tissues were obtained fresh from the local abattoir immediatel...

<ol>
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Comprehensive proteome profiling of a diverse range of ocular samples is an important and indispensable first step to elucidate the molecular mechanisms and signaling pathways implicated in health and disease. In order to obtain high quality data and to ensure the reproducibility of results obtained from these analyses, the preceding sample preparation steps are crucial, as highlighted in a review by Mandal et al. that discussed in-depth the sample processing procedures for different parts of the eye employing two-dimens...

The advancement in the field of proteomics, which permits integrated and unsurpassed data collection power, has greatly revolutionized our understanding of the molecular mechanisms underlying certain disease conditions as well as in reflecting the physiological state of a specific cell population or tissue1,2,3,4. Proteomics has also proved to be an important platform in ophthalmic research owing to the sensitivity and unbiased analysis of different ocular samples that facilitated identification of potential disease markers for eventual diagnosis and prognosis, as evidenced elegantly by many studies in recent years, including some of ours1,5,6,7,8,9,10. However, it is often difficult to obtain human samples for proteomic analyses due to ethical reasons, especially considering the need for control material from healthy individuals for reliable comparative analyses. On the other hand, it is also challenging to obtain sufficient amount of samples for optimal and reliable mass spectrometric analyses. This is particularly crucial for mass-limited biological materials such as the micro-blood vessels of the eye. One such major retrobulbar blood vessel that plays pivotal roles in the regulation of ocular blood flow is the short posterior ciliary artery (sPCA). Any perturbation or anomalies in this vascular bed may result in severe clinical repercussions, which can lead to the pathogenesis of several sight-threatening diseases such as glaucoma and nonarteritic anterior ischemic optic neuropathy (NAION)11,12. However, there is a lack of studies elucidating the proteome changes in this arterial bed due to the above-mentioned drawbacks. Therefore, in recent years, the house swine (Sus scrofa domestica Linnaeus, 1758) has emerged as a good animal model in ophthalmic research owing to the high morphologic and phylogenetic similarities between humans and pigs13,14,15. Porcine ocular samples are easily available and most importantly, are more accurate representation of human tissues.
Considering the important role of these blood vessels in the eye, as well as the dearth of methodology catered for efficient protein extraction and analyses from these microvessels, we have previously characterized the proteome of the porcine sPCA using an in-house protocol that resulted in the identification of a high number of proteins16. Based on this study, we have further optimized and described in-depth our methodology in this article, which allows proteome analysis from minute amounts of samples using the porcine sPCA as model tissue. Albeit the main aim of this study was to establish a MS-compatible methodology for mass-limited ocular blood vessels, we have provided substantial experimental evidence that the described workflow can also be broadly applied to various tissue-based samples.
It is envisioned that this workflow will be instrumental for preparation of high-quality MS-compatible samples from small quantities of materials for comprehensive proteome analyses.

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			<td height="21" style="height:21px;width:436px;">A. Chemicals</td>
			<td style="width:281px;"></td>
			<td style="width:120px;"></td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1, 4-Dithiothreitol (DTT)</td>
			<td>Sigma-Aldrich</td>
			<td style="width:120px;">1.11474</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium bicarbonate (ABC, CH&#8325;NO&#8323;)</td>
			<td>Sigma-Aldrich</td>
			<td>5.33005</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Calcium chloride dihydrate (CaCl2)&#160;</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>5239.1</td>
			<td>2.5 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#39;s phosphate-buffered saline (PBS)&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific</td>
			<td>14190169</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Formic acid (CH2O2)</td>
			<td style="width:281px;">AppliChem</td>
			<td style="width:120px;">A0748</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">HPLC-grade acetonitrile (ACN, C2H3N)</td>
			<td style="width:281px;">AppliChem</td>
			<td style="width:120px;">A1605</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">HPLC-grade methanol (CH3OH)</td>
			<td style="width:281px;">Fisher Scientific</td>
			<td style="width:120px;">M/4056/17</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HPLC-grade water&#160;</td>
			<td style="width:281px;">AppliChem</td>
			<td style="width:120px;">A1589</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Iodoacetamide (IAA)</td>
			<td>Sigma-Aldrich</td>
			<td style="width:120px;">I6125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Kalium chloride (KCl)&#160;</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>6781.1</td>
			<td>4.7 mM&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Kalium dihydrogen phosphate (KH2PO4)</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>3904.2</td>
			<td>1.2 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LC-MS-grade acetic acid</td>
			<td style="width:281px;">&#160;Carl Roth&#160;</td>
			<td style="width:120px;">AE69.1</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Magnesium sulphate (MgSO4)&#160;&#160;</td>
			<td>&#160;Carl Roth&#160;</td>
			<td style="width:120px;">261.2</td>
			<td>1.2 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE Antioxidant</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td style="width:120px;">NP0005</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE LDS Sample buffer&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0007</td>
			<td>4x</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE MES SDS Running Buffer&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0002</td>
			<td>20x</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE Sample reducing agent&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0004</td>
			<td>10x</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SeeBlue Plus2 pre-stained protein standard&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td style="width:120px;">LC5925</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sequencing grade modified trypsin</td>
			<td style="width:281px;">Promega</td>
			<td style="width:120px;">V5111</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium chloride (NaCl)</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>9265.2</td>
			<td>118.3 mM&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Sodium hydrogen carbonate (NaHCO3)</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>965.3</td>
			<td>25 mM&#160;</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Trifluoroacetic acid (TFA,&#160; C2HF3O2)</td>
			<td style="width:281px;">Merck Millipore</td>
			<td style="width:120px;">108178</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#945;-(D)-(+)- Glucose monohydrate</td>
			<td>&#160;Carl Roth&#160;</td>
			<td>6780.1</td>
			<td>11 mM&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">B. Reagents and Kits</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">0.5mm zirconium oxide beads&#160;</td>
			<td style="width:281px;">Next Advance</td>
			<td style="width:120px;">ZROB05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1.0mm zirconium oxide beads&#160;</td>
			<td style="width:281px;">Next Advance</td>
			<td style="width:120px;">ZROB10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Colloidal Blue Staining&#160; Kit</td>
			<td style="width:281px;">Thermo Fisher Scientific (Invitrogen)</td>
			<td style="width:120px;">LC6025</td>
			<td>To stain 25 mini gels per kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NuPAGE 4-12 % Bis-Tri gels</td>
			<td>Thermo Fisher Scientific (Invitrogen)</td>
			<td>NP0321BOX</td>
			<td>1.0 mm, 10-well</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pierce Bicinchoninic Acid (BCA) Protein Assay Kit&#160;</td>
			<td style="width:281px;">Thermo Fisher Scientific</td>
			<td style="width:120px;">23227</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ProteoExtract Transmembrane Protein Extraction Kit, TM-PEK</td>
			<td style="width:281px;">Merck Millipore</td>
			<td style="width:120px;">71772-3</td>
			<td>20 reactions per kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tissue Protein Extraction Reagent (T-PER)</td>
			<td style="width:281px;">Thermo Scientific</td>
			<td style="width:120px;">78510</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">C. Tools</td>
			<td style="width:281px;"></td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">96-well V-bottom plates</td>
			<td style="width:281px;">Greiner Bio-One</td>
			<td style="width:120px;">651180</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Corning 96-well flat-bottom plates</td>
			<td style="width:281px;">Sigma-Aldrich</td>
			<td style="width:120px;">CLS3595-50EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Disposable microtome blades</td>
			<td>pfm Medical</td>
			<td>207500014</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Disposable scalpels #21</td>
			<td>pfm Medical</td>
			<td>200130021</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dissection pins&#160;</td>
			<td style="width:281px;">Carl Roth</td>
			<td style="width:120px;">PK47.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Extra Fine Bonn Scissors</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td style="width:120px;">14084-08</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Falcon conical centrifuge tubes (50 mL)</td>
			<td>Fisher Scientific</td>
			<td>14-432-22</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Mayo scissors, Tough cut</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td style="width:120px;">14130-17</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Precision tweezers</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td>11251-10</td>
			<td>Type 5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Precision tweezers, straight with extra fine tips</td>
			<td style="width:281px;">Carl Roth</td>
			<td>LH53.1</td>
			<td>Type 5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Self-adhesive sealing films for microplates</td>
			<td style="width:281px;">Ratiolab (vWR)</td>
			<td style="width:120px;">RATI6018412</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Standard pattern forceps</td>
			<td style="width:281px;">&#160;Fine Science Tools</td>
			<td style="width:120px;">11000-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Student Vannas spring scissors</td>
			<td>&#160;Fine Science Tools</td>
			<td>91501-09</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vannas capsulotomy scissors&#160;&#160;</td>
			<td style="width:281px;">Geuder</td>
			<td style="width:120px;">19760</td>
			<td>&#160;Straight, 77 mm</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">ZipTipC18 pipette tips</td>
			<td style="width:281px;">Merck Millipore</td>
			<td>ZTC18S096</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">D. Equipment and devices</td>
			<td style="width:281px;"></td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">150 &#215; 0.5 mm BioBasic C18 column</td>
			<td style="width:281px;">Thermo Scientific, Rockford, USA</td>
			<td style="width:120px;">72105-150565</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">30 &#215; 0.5 mm BioBasic C18 pre-column&#160;</td>
			<td style="width:281px;">Thermo Scientific, Rockford, USA</td>
			<td style="width:120px;">72105-030515</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Amicon Ultra-0.5 3K Centrifugal Filter Devices&#160;</td>
			<td style="width:281px;">Merck Millipore</td>
			<td style="width:120px;">UFC500396</td>
			<td>Pack of 96.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Analytical balance</td>
			<td>Sartorius</td>
			<td>H51</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Autosampler&#160;</td>
			<td>CTC Analytics AG, Zwingen, Switzerland</td>
			<td style="width:120px;">HTS Pal</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BBY24M Bullet Blender Storm&#160;</td>
			<td style="width:281px;">Next Advance</td>
			<td style="width:120px;">NA-BB-25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Eppendorf concentrator, model 5301</td>
			<td style="width:281px;">Sigma-Aldrich</td>
			<td style="width:120px;">Z368172</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Eppendorf microcentrifuge, model 5424</td>
			<td style="width:281px;">Fisher Scientific</td>
			<td style="width:120px;">05-403-93</td>
			<td>Non-refrigerated</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heraeus Primo R Centrifuge</td>
			<td style="width:281px;">Thermo Scientific</td>
			<td style="width:120px;">75005440</td>
			<td>Refrigerated</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Labsonic M Ultrasonic homogenizer&#160;</td>
			<td style="width:281px;">Sartorius</td>
			<td style="width:120px;">BBI-8535027</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LC-MS pump, model Rheos Allegro</td>
			<td style="width:281px;">Thermo Scientific, Rockford, USA</td>
			<td style="width:120px;">22080</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LTQ Orbitrap XL mass spectrometer&#160;</td>
			<td>Thermo Scientific, Bremen, Germany</td>
			<td style="width:120px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Multiskan Ascent plate reader&#160;</td>
			<td style="width:281px;">Thermo Labsystems</td>
			<td style="width:120px;">v2.6</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Rotator with vortex&#160;</td>
			<td style="width:281px;">neoLab</td>
			<td style="width:120px;">7-0045</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Titanium probe (&#216; 0.5mm, 80mm long)</td>
			<td style="width:281px;">Sartorius</td>
			<td style="width:120px;">BBI-8535612</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic bath, type RK 31</td>
			<td style="width:281px;">Bandelin</td>
			<td style="width:120px;">329</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Xcell Surelock Mini Cell</td>
			<td>Life Technologies</td>
			<td>El0001</td>
			<td></td>
		</tr>
	</tbody>
</table>

sample preparation for mass-spectrometry-based proteomics analysis of ocular microvessels

The use of isolated ocular blood vessels in vitro to decipher the pathophysiological state of the eye using advanced technological approaches has greatly expanded our understanding of certain diseases. Mass spectrometry (MS)-based proteomics has emerged as a powerful tool to unravel alterations in the molecular mechanisms and protein signaling pathways in the vascular beds in health and disease. However, sample preparation steps prior to MS analyses are crucial to obtain reproducible results and in-depth elucidation of the complex proteome. This is particularly important for preparation of ocular microvessels, where the amount of sample available for analyses is often limited and thus, poses a challenge for optimum protein extraction. This article endeavors to provide an efficient, rapid and robust protocol for sample preparation from an exemplary retrobulbar ocular vascular bed employing the porcine short posterior ciliary arteries. The present method focuses on protein extraction procedures from both the supernatant and pellet of the sample following homogenization, sample cleaning with centrifugal filter devices prior to one-dimensional gel electrophoresis and peptide purification steps for label-free quantification in a liquid chromatography-electrospray ionization-linear ion trap-Orbitrap MS system. Although this method has been developed specifically for proteomics analyses of ocular microvessels, we have also provided convincing evidence that it can also be readily employed for other tissue-based samples.

Limited sample availability is one of the major drawbacks in ophthalmic research. Correspondingly, extraction methods for optimum protein yield from small amounts of samples such as ocular blood vessels are often debatable. To date, there is a paucity of methods catered particularly for protein extraction from retrobulbar blood vessels. Therefore, as a first step in method optimization and as a proof-of-principle to compare the efficacy and robustness of several commonly employed protein ...

Watch this Scientific Journal Video about Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels at JoVE.com

Sample Preparation for Mass-spectrometry-based Proteomics Analysis of Ocular Microvessels

Proteome characterization of ocular microvascular beds is pivotal for in-depth understanding of many ocular pathologies in humans. This study demonstrates an effective, rapid, and robust method for protein extraction and sample preparation from small blood vessels employing the porcine short posterior ciliary arteries as model vessels for mass-spectrometry-based proteomics analyses.

The use of isolated ocular blood vessels in vitro to decipher the pathophysiological state of the eye using advanced technological approaches has greatly ...

The preparation of high-quality mass-spectrometry-compatible samples for comprehensive proteome analysis of ocular samples is critical to elucidate the molecular mechanisms and signaling pathways implicated in health and disease. The described work flow represents a simple yet robust approach to stringent sample preparation steps catered specifically for analysis of mass-limited samples such as ocular micro blood vessels. Although the main aim of the study is to establish an MS-compatible methodology for ocular blood vessels, the described work flow can be broadly applied to various cell-and tissue-based samples.Generally, individuals new to this method may struggle because the identification and isolation of the chosen short posterior ciliary artery, or SPCA branches, can be challenging. Fresh porcine eyes, together with optic nerve and extraocular tissues, were obtained from the local abattoir immediately post-mortem. Place the eye globe in a dissection chamber containing ice-cold Krebs-Henseleit buffer.Carefully cut away surrounding muscle and tissues with a pair of sharp Mayo scissors. Make an incision with a scalpel, and cut the globe along the equatorial plane with a pair of sharp Mayo scissors until the eye is separated into the anterior and posterior halves. Remove as much vitreous body as possible from the posterior half of the eye using a pair of standard pattern forceps.After using dissection pins to carefully pin down the posterior half of the eye, gently cut away the connective tissues surrounding the optic nerve, to expose the underlying retrobulbar vasculature with a pair of student Vannas spring scissors. Isolate the paraoptic and distal short posterior ciliary artery together with the surrounding connective tissues with a pair of type five precision tweezers and Vannas capsulotomy scissors. Gently remove connective tissues from the arterial segments using extra fine tipped tweezers and scissors before rinsing the isolated arteries in ice-cold PBS to remove contaminants and blood residues.Pool arteries from two eyes to obtain one biological replicate, then weigh the samples using an analytical balance. To each tube, add a mixture of 0.5 and one-millimeter zirconium oxide beads followed by tissue protein extraction reagent. Now, load the sample tubes into a blender homogenizer.Set the timer to two minutes, set the speed level to six, and start homogenization. After running, check the samples for complete homogenization and keep samples on ice in between each run. Repeat the cycle until samples are completely homogenized.Carefully pipette homogenate into fresh microcentrifuge tubes. Centrifuge the samples at 10, 000 times G for 20 minutes at four degrees Celsius to pellet insoluble proteins. Carefully pipette the supernatant containing the soluble proteins without touching the pellet layer, and transfer into fresh microcentrifuge tubes.Add 200 microliters of Extraction Buffer 2A and five microliters of protease inhibitor cocktail to each pellet sample. Then, suspend the pellet several times with a pipette. Use an ultrasonic homogenizer to completely homogenize the pellet.Set the amplitude to 60 and cycle to one. Use a probe made of titanium, which is appropriate for homogenization of samples with small volumes. Immerse the probe in the pellet and extraction buffer mixture on ice, and press the start button.Sonicate the sample until the pellet clumps are completely homogenized, pausing for a few seconds between each sonication. Check for complete homogenization visually. Mix the homogenate several times with a pipette to ensure that there are no clumps.Use centrifugal filter devices with three-kilodalton cutoff for this procedure. Insert the three-kilodalton cutoff filter unit into a microcentrifuge tube. Pipette 200 microliters of sample homogenate to one filter device, and add 200 microliters of deionized water into the same filter.After capping it securely, place the filter unit into a centrifuge, and spin for 14, 000 times G for 15 minutes at four degrees Celsius. After centrifugation, separate the filter unit containing the sample concentrate from the microcentrifuge tube containing the filtrate, discarding the filtrate. Reconstitute the concentrate by adding 400 microliters of deionized water into the filter unit.After repeating filtration three times, carefully pipette the cleaned sample concentrate into a clean microtube. Prepare the samples for one-dimensional gel electrophoresis as listed in the text protocol, and mix well with a pipette. Heat the samples at 70 degrees Celsius in a dry block heater for 15 minutes, and cool to room temperature.Carefully load 50 micrograms of sample per lane using a pipette, as well as the prestained protein standard as a molecular mass marker. Run the gels for approximately 60 minutes at a constant voltage of 175 volts. At the end of the run, carefully remove the gel from the cassette plate using a gel knife, and transfer the gel into a gel staining box.Perform fixing and staining of the gel as described in the text protocol. Shake the gels in the staining solution overnight for best overall results. Carefully decant the staining solution and replace with 200 milliliters of deionized water before shaking the gels for at least seven to eight hours in water to clear the background.Excise the protein bands from the gel with clean new microtome blades. Cut the band into small pieces, and carefully transfer the gel pieces into 1.5-milliliter microcentrifuge tubes. Add 500 microliters of destaining solution containing 100-millimolar ammonium bicarbonate and acetonitrile.Incubate the samples at room temperature for 30 minutes, with occasional shaking. Carefully pipette out the destaining solution. Check visually for any tubes with residual stain, and repeat this step if gel pieces are still stained blue.Add approximately 400 microliters of freshly prepared DTT solution, and incubate at 56 degrees Celsius for 30 minutes. After discarding the reducing solution with a pipette, add approximately 400 microliters of freshly prepared IAA solution, and incubate in the dark at room temperature for 30 minutes. Remove the alkylating buffer with a pipette and discard.Add 500 microliters of neat acetonitrile at room temperature for 10 to 15 minutes, until the gel pieces shrink and become opaque. Pipette out the acetonitrile, and air-dry the gel pieces for five to 10 minutes under the hood. Then, pipette 50 microliters of trypsin solution into each tube to completely cover the gel pieces, and incubate the tubes at four degrees Celsius.After 30 minutes, add sufficient volume of trypsin buffer to completely cover the gel pieces if necessary. Incubate the samples overnight at 37 degrees Celsius. To perform peptide extraction, carefully pipette the extracted peptide solution from the tubes and transfer to clean microtubes.Dry the supernatant in a centrifugal vacuum evaporator. Add 100 microliters of extraction buffer to each tube with gel pieces, and incubate for 30 minutes with shaking. Pipette the supernatant into the same microtubes containing the extracted peptides according to their respective bands, and dry down in a vacuum centrifuge.Proceed to peptide purification and liquid chromatography-electrospray ionization MS/MS analyses as described in the text protocol. The total amount of proteins in samples extracted with each type of detergent is depicted here. The highest yield came from tissues extracted with tissue protein extraction buffer, followed by DDM, CHAPS, ASB-14, and the lowest yield from ACN and TFA.Consistently, the total proteins identified were also the highest in the tissue protein extraction buffer extracted sample, and followed same trend as the total yield. Shown here is the comparison of the one-dimension gel electrophoresis protein profiles of SPCA, before and after being subjected to the optimized sample preparation and cleaning steps. Overall, a high degree of smearing and poor separation of the protein bands was observed at lane three.This profile demonstrates that the samples may contain extraction reagent, and also contaminants such as lipids and cellular debris. However, the SPCA samples that were separated into supernatant and pellet, and then subjected to the optimized protocol, resulted in exemplary one-dimensional gel electrophoresis profiles. The optimized method for rapid, robust, and efficient protein extraction from ocular microvessels can also be readily applied to other tissue-based samples.Shown here are protein profiles of the supernatant and the pellet of murine brain and cardiac tissue samples. While attempting this procedure, it is important to remember to subject the samples to complete homogenization, to separate the supernatant from the pellet, and to remove the contaminants and the extraction reagents. After its development, this technique paved the way for researchers in the field of experimental and translational ophthalmology to thoroughly explore the proteome of oscular vasculature using porcine eyes as a model.

sample-preparation-for-mass-spectrometry-based-proteomics-analysis

Research

JoVE Journal

Biology

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Plasma membrane microdomains are features based on the physical properties of the lipid and sterol environment and have particular roles in signaling processes. Extracting sterol-enriched membrane microdomains from plant cells for proteomic analysis is a difficult task mainly due to multiple preparation steps and sources for contaminations from other cellular compartments. The plasma membrane constitutes only about 5-20% of all the membranes in a plant cell, and therefore isolation of highly purified plasma membrane fraction is challenging. A frequently used method involves aqueous two-phase partitioning in polyethylene glycol and dextran, which yields plasma membrane vesicles with a purity of 95% 1. Sterol-rich membrane microdomains within the plasma membrane are insoluble upon treatment with cold nonionic detergents at alkaline pH. This detergent-resistant membrane fraction can be separated from the bulk plasma membrane by ultracentrifugation in a sucrose gradient 2. Subsequently, proteins can be extracted from the low density band of the sucrose gradient by methanol/chloroform precipitation. Extracted protein will then be trypsin digested, desalted and finally analyzed by LC-MS/MS. Our extraction protocol for sterol-rich microdomains is optimized for the preparation of clean detergent-resistant membrane fractions from Arabidopsis thaliana cell cultures.
We use full metabolic labeling of Arabidopsis thaliana suspension cell cultures with K15NO3 as the only nitrogen source for quantitative comparative proteomic studies following biological treatment of interest 3. By mixing equal ratios of labeled and unlabeled cell cultures for joint protein extraction the influence of preparation steps on final quantitative result is kept at a minimum. Also loss of material during extraction will affect both control and treatment samples in the same way, and therefore the ratio of light and heave peptide will remain constant. In the proposed method either labeled or unlabeled cell culture undergoes a biological treatment, while the other serves as control 4.

Metabolic Labeling and Membrane Fractionation for Comparative Proteomic Analysis of Arabidopsis thaliana Suspension Cell Cultures

Here we describe a robust method for the fractionation of plant plasma membranes into detergent resistant and detergent soluble membranes based on a mixture of unlabeled and in vivo fully 15N labeled Arabidopsis thaliana cell cultures. The procedure is applied for comparative proteomic studies to understand signaling processes.

Plasma membrane microdomains are features based on the physical properties of the lipid and sterol environment and have particular roles in signaling ...

Proteomic Sample Preparation from Formalin Fixed and Paraffin Embedded Tissue

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale quantitative analysis of formalin fixed and paraffin embedded (FFPE) tissue. The procedure comprises four distinct steps. The first one is the preparation of sections from the FFPE material and microdissection of cells of interest. In the second step the isolated cells are lysed and processed using 'filter aided sample preparation' (FASP) technique. In this step, proteins are depleted from reagents used for the sample lysis and are digested in two-steps using endoproteinase LysC and trypsin. 
After each digestion, the peptides are collected in separate fractions and their content is determined using a highly sensitive fluorescence measurement. Finally, the peptides are fractionated on 'pipette-tip' microcolumns. The LysC-peptides are separated into 4 fractions whereas the tryptic peptides are separated into 2 fractions. In this way prepared samples allow analysis of proteomes from minute amounts of material to a depth of 10,000 proteins. Thus, the described workflow is a powerful technique for studying diseases in a system-wide-fashion as well as for identification of potential biomarkers and drug targets.

Archival formalin fixed and paraffin embedded (FFPE) clinical samples are valuable material for investigation of diseases. Here we demonstrate a sample preparation workflow allowing in-depth proteomic analysis of microdissected FFPE tissue.

Preserved clinical material is a unique source for proteomic investigation of human disorders. Here we describe an optimized protocol allowing large scale ...

Enrichment of Extracellular Matrix Proteins from Tissues and Digestion into Peptides for Mass Spectrometry Analysis

The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins that provides biophysical and biochemical cues that are major regulators of cell proliferation, survival, migration, etc. The ECM plays important roles in development and in diverse pathologies including cardio-vascular and musculo-skeletal diseases, fibrosis, and cancer. Thus, characterizing the composition of ECMs of normal and diseased tissues could lead to the identification of novel prognostic and diagnostic biomarkers and potential novel therapeutic targets. However, the very nature of ECM proteins (large in size, cross-linked and covalently bound, heavily glycosylated) has rendered biochemical analyses of ECMs challenging. To overcome this challenge, we developed a method to enrich ECMs from fresh or frozen tissues and tumors that takes advantage of the insolubility of ECM proteins. We describe here in detail the decellularization procedure that consists of sequential incubations in buffers of different pH and salt and detergent concentrations and that results in 1) the extraction of intracellular (cytosolic, nuclear, membrane and cytoskeletal) proteins and 2) the enrichment of ECM proteins. We then describe how to deglycosylate and digest ECM-enriched protein preparations into peptides for subsequent analysis by mass spectrometry.

This protocol describes a procedure for enriching ECM proteins from tissues or tumors and deglycosylating and digesting the ECM-enriched preparations into peptides to analyze their protein composition by mass spectrometry.

The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins that provides biophysical and biochemical cues that are major regulators of ...

Sample Preparation for Mass Cytometry Analysis

Mass cytometry utilizes antibodies conjugated with heavy metal labels, an approach that has greatly increased the number of parameters and opportunities for deep analysis well beyond what is possible with conventional fluorescence-based flow cytometry. As with any new technology, there are critical steps that help ensure the reliable generation of high-quality data. Presented here is an optimized protocol that incorporates multiple techniques for the processing of cell samples for mass cytometry analysis. The methods described here will help the user avoid common pitfalls and achieve consistent results by minimizing variability, which can lead to inaccurate data. To inform experimental design, the rationale behind optional or alternative steps in the protocol and their efficacy in uncovering new findings in the biology of the system being investigated is covered. Lastly, representative data is presented to illustrate expected results from the techniques presented here.

This article describes the collection and processing of samples for mass cytometry analysis.

Mass cytometry utilizes antibodies conjugated with heavy metal labels, an approach that has greatly increased the number of parameters and opportunities ...

An Alternative Approach for Sample Preparation with Low Cell Number for TEM Analysis

Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, especially cells in suspension such as hematopoietic stem cells (HSCs), remains limited due to the requirement of a high cell number during sample preparation. There are a few cytospin or monolayer approaches for TEM analysis from scarce samples, but these approaches fail to get significant quantitative data from the limited number of cells. Here, an alternative and novel approach for sample preparation in TEM studies is described for rare cell populations that enables quantitative analysis.
A relatively low cell number, i.e., 10,000 HSCs, was successfully used for TEM analysis compared to the millions of cells typically used for TEM studies. In particular, Evans blue staining was performed after paraformaldehyde-glutaraldehyde (PFA-GA) fixation to visualize the tiny cell pellet, which facilitated embedding in agarose. Clusters of numerous cells were observed in ultra-thin sections. The cells had a well preserved morphology, and the ultra-structural details of the Golgi complex and several mitochondria were visible. This efficient, easy and reproducible protocol allows sample preparation from a low cell number and can be used for qualitative and quantitative TEM analysis on rare cell populations from limited biological samples.

Here, we present a protocol to prepare samples with low cell numbers for transmission electron microscopy (TEM) analysis.

Transmission electron microscopy (TEM) provides details of the cellular organization and ultrastructure. However, TEM analysis of rare cell populations, ...

Sample Preparation and Imaging of Exosomes by Transmission Electron Microscopy

Exosomes are nano-sized extracellular vesicles secreted by body fluids and are known to represent the characteristics of cells that secrete them. The contents and morphology of the secreted vesicles reflect cell behavior or physiological status, for example cell growth, migration, cleavage, and death. The exosomes&#39; role may depend highly on size, and the size of exosomes varies from 30 to 300 nm. The most widely used method for exosome imaging is negative staining, while other results are based on Cryo-Transmission Electron Microscopy, Scanning Electron Microscopy, and Atomic Force Microscopy. The typical exosome&#39;s morphology assessed through negative staining is a cup-shape, but further details are not yet clear. An exosome well-characterized through structural study is necessary particular in medical and pharmaceutical fields. Therefore, function-dependent morphology should be verified by electron microscopy techniques such as labeling a specific protein in the detailed structure of exosome. To observe detailed structure, ultrathin sectioned images and negative stained images of exosomes were compared. In this protocol, we suggest transmission electron microscopy for the imaging of exosomes including negative staining, whole mount immuno-staining, block preparation, thin section, and immuno-gold labelling.

This protocol describes the various techniques necessary for transmission electron microscopy including negative staining, ultrathin sectioning for detailed structure, and immuno-gold labelling to determine the positions of specific proteins in exosomes.

Exosomes are nano-sized extracellular vesicles secreted by body fluids and are known to represent the characteristics of cells that secrete them. The ...

Miniaturized Sample Preparation for Transmission Electron Microscopy

Due to recent technological progress, cryo-electron microscopy (cryo-EM) is rapidly becoming a standard method for the structural analysis of protein complexes to atomic resolution. However, protein isolation techniques and sample preparation methods for EM remain a bottleneck. A relatively small number (100,000 to a few million) of individual protein particles need to be imaged for the high-resolution analysis of proteins by the single particle EM approach, making miniaturized sample handling techniques and microfluidic principles feasible.
A miniaturized, paper-blotting-free EM grid preparation method for sample pre-conditioning, EM grid priming and post processing that only consumes nanoliter-volumes of sample is presented. The method uses a dispensing system with sub-nanoliter precision to control liquid uptake and EM grid priming, a platform to control the grid temperature thereby determining the relative humidity above the EM grid, and a pick-and-plunge-mechanism for sample vitrification. For cryo-EM, an EM grid is placed on the temperature-controlled stage and the sample is aspirated into a capillary. The capillary tip is positioned in proximity to the grid surface, the grid is loaded with the sample and excess is re-aspirated into the microcapillary. Subsequently, the sample film is stabilized and slightly thinned by controlled water evaporation regulated by the offset of the platform temperature relative to the dew-point. At a given point the pick-and-plunge mechanism is triggered, rapidly transferring the primed EM grid into liquid ethane for sample vitrification. Alternatively, sample-conditioning methods are available to prepare nanoliter-sized sample volumes for negative stain (NS) EM.
The methodologies greatly reduce sample consumption and avoid approaches potentially harmful to proteins, such as the filter paper blotting used in conventional methods. Furthermore, the minuscule amount of sample required allows novel experimental strategies, such as fast sample conditioning, combination with single-cell lysis for &#34;visual proteomics,&#34; or &#34;lossless&#34; total sample preparation for quantitative analysis of complex samples.

An instrument and methods for the preparation of nanoliter-sized sample volumes for transmission electron microscopy is presented. No paper-blotting steps are required, thus avoiding the detrimental consequences this can have for proteins, significantly reducing sample loss and enabling the analysis of single cell lysate for visual proteomics.

Due to recent technological progress, cryo-electron microscopy (cryo-EM) is rapidly becoming a standard method for the structural analysis of protein ...

Comprehensive Workflow of Mass Spectrometry-based Shotgun Proteomics of Tissue Samples

Recent advances in mass spectrometry have resulted in deep proteomic&#160;analysis along with the generation of&#160;robust and&#160;reproducible datasets. However, despite the considerable technical advancements, sample preparation from biospecimens such as patient blood, CSF, and tissue still poses considerable challenges. For identifying biomarkers, tissue proteomics often provides an attractive sample source to translate the research findings from the bench to the clinic. It can reveal potential candidate biomarkers for early diagnosis of cancer and neurodegenerative diseases such as Alzheimer&#39;s disease, Parkinson&#39;s disease, etc. Tissue proteomics also yields a wealth of systemic information based on the abundance of proteins and helps to address interesting biological questions.
Quantitative proteomics analysis can be grouped into two broad categories: a label-based and a label-free approach. In the label-based approach, proteins or peptides are labeled using stable isotopes such as SILAC (stable isotope labeling with amino acids in cell culture) or by chemical tags such as ICAT (isotope-coded affinity tags), TMT (tandem mass tag) or iTRAQ (isobaric tag for relative and absolute quantitation). Label-based approaches have the advantage of more accurate quantitation of proteins and using isobaric labels, multiple samples can be analyzed in a single experiment. The label-free approach provides a cost-effective alternative to label-based approaches. Hundreds of patient samples belonging to a particular cohort can be analyzed and compared with other cohorts based on clinical features. Here, we have described an optimized quantitative proteomics workflow for tissue samples using label-free and label-based proteome profiling methods, which is crucial for applications in life sciences, especially biomarker discovery-based projects.

The described protocol provides an optimized quantitative proteomics analysis of tissue samples using two approaches: label-based and label free quantitation. Label-based approaches have the advantage of more accurate quantitation of proteins, while a label-free approach is more cost-effective and used to analyze hundreds of samples of a cohort.

Recent advances in mass spectrometry have resulted in deep proteomic&#160;analysis along with the generation of&#160;robust and&#160;reproducible ...

Efficient and Consistent Generation of Retinal Pigment Epithelium/Choroid Flatmounts from Human Eyes for Histological Analysis

The retinal pigment epithelium (RPE) and retina are functionally and structurally connected tissues that work together to regulate light perception and vision. Proteins on the RPE apical surface are tightly associated with proteins on the photoreceptor outer segment surface, making it difficult to consistently separate the RPE from the photoreceptors/retina. We developed a method to efficiently separate the retina from the RPE of human eyes to generate complete RPE/choroid and retina flatmounts for separate cellular analysis of the photoreceptors and RPE cells. An intravitreal injection of a high-osmolarity solution of D-mannitol, a sugar not transported by the RPE, induced the separation of the RPE and retina across the entire posterior chamber without causing damage to the RPE cell junctions. No RPE patches were observed attached to the retina. Phalloidin labeling of actin showed RPE shape preservation and allowed morphometric analysis of the entire epithelium. An artificial intelligence (AI)-based software was developed to accurately recognize and segment the RPE cell borders and quantify 30 different shape metrics. This dissection method is highly reproducible and can be easily extended to other animal models.

We describe a method to efficiently separate retinal pigment epithelium (RPE) from the retina in human eyes and generate whole RPE/choroid flatmounts for histological and morphometric analyses of the RPE.

The retinal pigment epithelium (RPE) and retina are functionally and structurally connected tissues that work together to regulate light perception and ...

Single-Cell Proteomics Preparation for Mass Spectrometry Analysis Using Freeze-Heat Lysis and an Isobaric Carrier

Single-cell proteomics analysis requires sensitive, quantitatively accurate, widely accessible, and robust methods. To meet these requirements, the Single-Cell ProtEomics (SCoPE2) protocol was developed as a second-generation method for quantifying hundreds to thousands of proteins from limited samples, down to the level of a single cell. Experiments using this method have achieved quantifying over 3,000 proteins across 1,500 single mammalian cells (500-1,000 proteins per cell) in 10 days of mass spectrometer instrument time. SCoPE2 leverages a freeze-heat cycle for cell lysis, obviating the need for clean-up of single cells and consequently reducing sample losses, while expediting sample preparation and simplifying its automation. Additionally, the method uses an isobaric carrier, which aids protein identification and reduces sample losses.
This video protocol provides detailed guidance to enable the adoption of automated single-cell protein analysis using only equipment and reagents that are widely accessible. We demonstrate critical steps in the procedure of preparing single cells for proteomic analysis, from harvesting up to injection to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Additionally, viewers are guided through the principles of experimental design with the isobaric carrier, quality control for both isobaric carrier and single-cell preparations, and representative results with a discussion of limitations of the approach.

In this protocol, we describe how to prepare mammalian cells for single-cell proteomics analysis via mass spectrometry using commercially available reagents and equipment, with options for both manual and automatic pipetting.

Single-cell proteomics analysis requires sensitive, quantitatively accurate, widely accessible, and robust methods. To meet these requirements, the ...