وأيد هذا العمل من قبل شهادة جائزة بوروز ويلكوم في واجهة العلم (ARD)، والمعاهد الوطنية للصحة من خلال مدير المعاهد الوطنية للصحة الجديد المبتكر برنامج جائزة-1-DP2 OD007078 (ARD)، وباوز وليام الابن ستانفورد زمالة دراسات عليا (ASA )، والقلب والأوعية الدموية ستانفورد زمالة معهد Predoctoral الأصغر سنا (JC). المؤلفان بالشكر جيمس Spudich لإعارة معدات الفحص المجهري.

<ol>
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K., Wang, Y. M., Huang, L. S., Lin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomic+force+microscopy:+determination+of+unbinding+force,+off+rate+and+energy+barrier+for+protein-ligand+interaction.">Atomic force microscopy: determination of unbinding force, off rate and energy barrier for protein-ligand interaction.</a> Micron. 38, 446-461 (2007).</li><li>Smith, S. B., Finzi, L., Bustamante, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+mechanical+measurements+of+the+elasticity+of+single+DNA+molecules+by+using+magnetic+beads.">Direct mechanical measurements of the elasticity of single DNA molecules by using magnetic beads.</a> Science. 258, 1122-1126 (1992).</li><li>Tanase, M., Biais, N., Sheetz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+tweezers+in+cell+biology.">Magnetic tweezers in cell biology.</a> Methods Cell Biol. 83, 473-493 (2007).</li><li>Neuman, K. C., Nagy, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-molecule+force+spectroscopy:+optical+tweezers,+magnetic+tweezers+and+atomic+force+microscopy.">Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy.</a> Nat. Methods. 5, 491-505 (2008).</li><li>Frank, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stabilization+of+short+collagen-like+triple+helices+by+protein+engineering.">Stabilization of short collagen-like triple helices by protein engineering.</a> J. Mol. Biol. 308, 1081-1089 (2001).</li><li>Stetefeld, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collagen+stabilization+at+atomic+level:+crystal+structure+of+designed+(GlyProPro)10foldon.">Collagen stabilization at atomic level: crystal structure of designed (GlyProPro)10foldon.</a> Structure. 11, 339-346 (2003).</li><li>Chung, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collagenase+unwinds+triple-helical+collagen+prior+to+peptide+bond+hydrolysis.">Collagenase unwinds triple-helical collagen prior to peptide bond hydrolysis.</a> EMBO J. 23, 3020-3030 (2004).</li><li>Bell, G. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Models+for+the+specific+adhesion+of+cells+to+cells.">Models for the specific adhesion of cells to cells.</a> Science. 200, 618-627 (1978).</li><li>Selvin, P. R., Ha, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Single-molecule techniques: a laboratory manual. , (2008).</li><li>Graneli, A., Yeykal, C. C., Prasad, T. K., Greene, E. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Organized+arrays+of+individual+DNA+molecules+tethered+to+supported+lipid+bilayers.">Organized arrays of individual DNA molecules tethered to supported lipid bilayers.</a> Langmuir. 22, 292-299 (2006).</li><li>Danilowicz, C., Greenfield, D., Prentiss, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissociation+of+ligand-receptor+complexes+using+magnetic+tweezers.">Dissociation of ligand-receptor complexes using magnetic tweezers.</a> Anal. Chem. 77, 3023-3028 (2005).</li><li>Zhang, X., Halvorsen, K., Zhang, C. Z., Wong, W. P., Springer, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanoenzymatic+cleavage+of+the+ultralarge+vascular+protein+von+Willebrand+factor.">Mechanoenzymatic cleavage of the ultralarge vascular protein von Willebrand factor.</a> Science. 324, 1330-1334 (2009).</li><li>Woodside, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomechanical+measurements+of+the+sequence-dependent+folding+landscapes+of+single+nucleic+acid+hairpins.">Nanomechanical measurements of the sequence-dependent folding landscapes of single nucleic acid hairpins.</a> Proc. Natl. Acad. Sci. U.S.A. 103, 6190-6195 (2006).</li><li>del Rio, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretching+single+talin+rod+molecules+activates+vinculin+binding.">Stretching single talin rod molecules activates vinculin binding.</a> Science. 323, 638-641 (2009).</li><li>Gosse, C., Croquette, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic+tweezers:+micromanipulation+and+force+measurement+at+the+molecular+level.">Magnetic tweezers: micromanipulation and force measurement at the molecular level.</a> Biophys. J. 82, 3314-3329 (2002).</li></ol>

الإعلان عن أي تضارب في المصالح.

هذا البروتوكول وصفا لاستخدام تقنية جديدة لجزيء واحد الكلاسيكية. ملاقط المغناطيسية تسمح متوسطة إلى عالية الإنتاجية المقايسات جزيء واحد بطريقة فعالة من حيث التكلفة. لكن، مثل كل التقنيات التجريبية هناك تحديات ومخاطر محتملة. القيود ...

<table border="1" style=";text-align:right;direction:rtl"><tbody><tr><td> اسم الكاشف </td><td> شركة </td><td> فهرس العدد </td></tr><tr><td> الدقيقة الغطاء الزجاجي # 1.5 (22x22) </td><td> VWR </td><td> 48366-067 </td></tr><tr><td> الدقيقة الغطاء الزجاجي # 1.5 (22x40) </td><td> VWR </td><td> 48393-048 </td></tr><tr><td> امدا الحمض النووي </td><td> إينفيتروجن </td><td> 25250-010 </td></tr><tr><td> T4 الحمض النووي يغاز </td><td> إينفيتروجن </td><td> 15224-041 </td></tr><tr><td> Microcon Ultracel YM-100 </td><td> ميليبور </td><td> 42413 </td></tr><tr><td> مكافحة Digoxigenin </td><td> روش تشخيص </td><td> 11-333-089-001 </td></tr><tr><td> توين 20 </td><td> سيغما </td><td> P9416-100ML </td></tr&gt; <tr><td> المضادة للجسم myc </td><td> إينفيتروجن </td><td> 46-0603 </td></tr><tr><td> ألبومين المصل البقري </td><td> سيغما </td><td> B4287-5G </td></tr><tr><td> Dynabeads M-280 Streptavidin </td><td> إينفيتروجن </td><td> 658.01D </td></tr><tr><td> Dynabeads MyOne T1 Streptavidin </td><td> إينفيتروجن </td><td> 658.01D </td></tr><tr><td> ف Aminophenylmercuric خلات </td><td> Calbiochem </td><td> 164610 </td></tr><tr><td> البيوتين Maleimide </td><td> سيجما ألدريتش </td><td> B1267 </td></tr><tr><td> وصفت البيوتين بنسبة ضئيلة </td><td> IDT الحمض النووي </td><td> عرف توليف </td></tr><tr><td> وصفت Digoxigenin بنسبة ضئيلة </td><td> IDT الحمض النووي </td><td> عرف توليف </td></tr><tr><td> الكولاجينالببتيد الجينات </td><td> الحمض النووي 2.0 </td><td> عرف توليف </td></tr><tr><td> MMP-1 [كدنا] </td><td> هارفارد قاعدة البيانات البلازميد </td><td></td></tr><tr><td> Z-مترجم </td><td> Thorlabs </td><td> MTS50 </td></tr><tr><td> تحكم المؤازرة للمترجم </td><td> Thorlabs </td><td> TDC001 </td></tr></tbody></table>

multiplexed single-molecule force proteolysis measurements using magnetic tweezers

الجيل والكشف عن القوى الميكانيكية تمثل جانبا من علم وظائف الأعضاء في كل مكان الخلية، وله صلة مباشرة الانبثاث سرطان 1، 2، وتصلب الشرايين التئام الجروح 3. في كل هذه الأمثلة، والخلايا على حد سواء ممارسة القوة على البيئة المحيطة بهم وإعادة تشكيلها في وقت واحد إنزيمي المصفوفة خارج الخلية (ECM). لقد أصبح تأثير قوى على ECM وبالتالي مساحة اهتماما كبيرا لما لها من أهمية على الأرجح في والبيولوجية والطبية 4-7. تقنيات جزيء واحد مثل الاحتباس بصري 8، ذرية المجهر قوة 9، وملاقط المغناطيسية 10،11 تسمح للباحثين للتحقيق في وظيفة من الإنزيمات على المستوى الجزيئي بما تمارسه القوات على البروتينات الفردية. من هذه التقنيات، ملاقط المغناطيسية (MT) جديرة بالملاحظة لتكلفتها المنخفضة وإنتاجية عالية. MT بذل القوات في نطاق PN 1-100 ~ ميلي ثانية واحدة ويمكن أن توفر القرار موقتا،الصفات التي تتم مطابقة تماما لدراسة آلية انزيم على مستوى واحد جزيء 12. هنا نحن الإبلاغ عن فحص MT موازاة جدا لدراسة تأثير القوة على التحلل البروتيني من جزيئات البروتين وحيد. نقدم المثال محددة من التحلل البروتيني من الببتيد الكولاجين مثلوثي بواسطة مصفوفة الفلزي 1 (MMP-1)، ومع ذلك، يمكن هذا الفحص تتكيف بسهولة لدراسة ركائز أخرى والبروتياز.

Watch this Scientific Journal Video about Multiplexed Single-molecule Force Proteolysis Measurements Using Magnetic Tweezers at JoVE.com

Multiplexed Single-molecule Force Proteolysis Measurements Using Magnetic Tweezers

في هذه المادة ونحن وصف استخدام ملاقط المغناطيسي لدراسة تأثير القوة على التحلل البروتيني الأنزيمية على الصعيد جزيء واحد بطريقة موازاة للغاية.

المضاعفة واحدة جزيء القياسات التحلل البروتيني باستخدام الملقط قوة مغناطيسية

The  generation and detection of mechanical forces is a ubiquitous aspect of cell physiology,  with direct relevance to cancer metastasis1, atherogenesis2 ...

multiplexed-single-molecule-force-proteolysis-measurements-using

Research

JoVE Journal

Bioengineering

11.5K Views.  Stanford University. في هذه المادة ونحن وصف استخدام ملاقط المغناطيسي لدراسة تأثير القوة على التحلل البروتيني الأنزيمية على الصعيد جزيء واحد بطريقة موازاة للغاية.

Video: Multiplexed Single-molecule Force Proteolysis Measurements Using Magnetic Tweezers

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers

Single-molecule techniques for stretching DNA of contour lengths less than a kilobase are fraught with experimental difficulties. However, many interesting biological events such as histone binding and protein-mediated looping of DNA1,2, occur on this length scale. In recent years, the mechanical properties of DNA have been shown to play a significant role in fundamental cellular processes like the packaging of DNA into compact nucleosomes and chromatin fibers3,4. Clearly, it is then important to understand the mechanical properties of short stretches of DNA. In this paper, we provide a practical guide to a single-molecule optical tweezing technique that we have developed to study the mechanical behavior of DNA with contour lengths as short as a few hundred basepairs.
The major hurdle in stretching short segments of DNA is that conventional optical tweezers are generally designed to apply force in a direction lateral to the stage5,6, (see Fig. 1). In this geometry, the angle between the bead and the coverslip, to which the DNA is tethered, becomes very steep for submicron length DNA. The axial position must now be accounted for, which can be a challenge, and, since the extension drags the microsphere closer to the coverslip, steric effects are enhanced. Furthermore, as a result of the asymmetry of the microspheres, lateral extensions will generate varying levels of torque due to rotation of the microsphere within the optical trap since the direction of the reactive force changes during the extension.
Alternate methods for stretching submicron DNA run up against their own unique hurdles. For instance, a dual-beam optical trap is limited to stretching DNA of around a wavelength, at which point interference effects between the two traps and from light scattering between the microspheres begin to pose a significant problem. Replacing one of the traps with a micropipette would most likely suffer from similar challenges. While one could directly use the axial potential to stretch the DNA, an active feedback scheme would be needed to apply a constant force and the bandwidth of this will be quite limited, especially at low forces.
We circumvent these fundamental problems by directly pulling the DNA away from the coverslip by using a constant force axial optical tweezers7,8. This is achieved by trapping the bead in a linear region of the optical potential, where the optical force is constant-the strength of which can be tuned by adjusting the laser power. Trapping within the linear region also serves as an all optical force-clamp on the DNA that extends for nearly 350 nm in the axial direction. We simultaneously compensate for thermal and mechanical drift by finely adjusting the position of the stage so that a reference microsphere stuck to the coverslip remains at the same position and focus, allowing for a virtually limitless observation period.

We illustrate the use of a constant force axial optical tweezers to explore the mechanical properties of short DNA molecules. By stretching DNA axially, we minimize steric hindrances and artifacts arising in conventional lateral manipulation, allowing us to study DNA molecules as short as ~100 nm.

تمتد سلاسل قصيرة من الحمض النووي مع ثابت القوة المحورية الملقط البصري

Single-molecule techniques for stretching DNA of contour lengths  less than a kilobase are fraught with experimental difficulties. However, many ...

Flexural Rigidity Measurements of Biopolymers Using Gliding Assays

Microtubules are cytoskeletal polymers which play a role in cell division, cell mechanics, and intracellular transport. Each of these functions requires microtubules that are stiff and straight enough to span a significant fraction of the cell diameter. As a result, the microtubule persistence length, a measure of stiffness, has been actively studied for the past two decades1. Nonetheless, open questions remain: short microtubules are 10-50 times less stiff than long microtubules2-4, and even long microtubules have measured persistence lengths which vary by an order of magnitude5-9.
	Here, we present a method to measure microtubule persistence length. The method is based on a kinesin-driven microtubule gliding assay10. By combining sparse fluorescent labeling of individual microtubules with single particle tracking of individual fluorophores attached to the microtubule, the gliding trajectories of single microtubules are tracked with nanometer-level precision. The persistence length of the trajectories is the same as the persistence length of the microtubule under the conditions used11. An automated tracking routine is used to create microtubule trajectories from fluorophores attached to individual microtubules, and the persistence length of this trajectory is calculated using routines written in IDL.
	This technique is rapidly implementable, and capable of measuring the persistence length of 100 microtubules in one day of experimentation. The method can be extended to measure persistence length under a variety of conditions, including persistence length as a function of length along microtubules. Moreover, the analysis routines used can be extended to myosin-based acting gliding assays, to measure the persistence length of actin filaments as well.

A method to measure the persistence length or flexural rigidity of biopolymers is described. The method uses a kinesin-driven microtubule gliding assay to experimentally determine the persistence length of individual microtubules and is adaptable to actin-based gliding assays.

قياسات جمود العاطفة من البوليمرات الحيوية باستخدام فحوصات الانزلاق

Microtubules are cytoskeletal polymers which  play a role in cell division, cell mechanics, and intracellular transport. Each of these functions requires ...

Investigating Receptor-ligand Systems of the Cellulosome with AFM-based Single-molecule Force Spectroscopy

Cellulosomes are discrete multienzyme complexes used by a subset of anaerobic bacteria and fungi to digest lignocellulosic substrates. Assembly of the enzymes onto the noncatalytic scaffold protein is directed by interactions among a family of related receptor-ligand pairs comprising interacting cohesin and dockerin modules. The extremely strong binding between cohesin and dockerin modules results in dissociation constants in the low picomolar to nanomolar range, which may hamper accurate off-rate measurements with conventional bulk methods. Single-molecule force spectroscopy (SMFS) with the atomic force microscope measures the response of individual biomolecules to force, and in contrast to other single-molecule manipulation methods (i.e.&#160;optical tweezers), is optimal for studying high-affinity receptor-ligand interactions because of its ability to probe the high-force regime (&#62;120 pN). Here we present our complete protocol for studying cellulosomal protein assemblies at the single-molecule level. Using a protein topology derived from the native cellulosome, we worked with enzyme-dockerin and carbohydrate binding module-cohesin (CBM-cohesin) fusion proteins, each with an accessible free thiol group at an engineered cysteine residue. We present our site-specific surface immobilization protocol, along with our measurement and data analysis procedure for obtaining detailed binding parameters for the high-affinity complex. We demonstrate how to quantify single subdomain unfolding forces, complex rupture forces, kinetic off-rates, and potential widths of the binding well. The successful application of these methods in characterizing the cohesin-dockerin interaction responsible for assembly of multidomain cellulolytic complexes is further described.

Cellulosomes are multienzyme complexes designed for digesting cellulose. AFM-based SMFS was used to study the mechanical properties and folding configuration of cellulosome-associated protein assemblies. We present a complete workflow for protein immobilization, data acquisition, and data analysis to study the interactions of individual receptor-ligand complexes involved in cellulosome assembly.

Cellulosomes are discrete multienzyme complexes used by a subset of anaerobic bacteria and fungi to digest lignocellulosic substrates. Assembly of the ...

Magnetic Tweezers for the Measurement of Twist and Torque

Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques include so-called force spectroscopy approaches such as atomic force microscopy, optical tweezers, flow stretching, and magnetic tweezers. Amongst these approaches, magnetic tweezers have distinguished themselves by their ability to apply torque while maintaining a constant stretching force. Here, it is illustrated how such a &#8220;conventional&#8221; magnetic tweezers experimental configuration can, through a straightforward modification of its field configuration to minimize the magnitude of the transverse field, be adapted to measure the degree of twist in a biological molecule. The resulting configuration is termed the freely-orbiting magnetic tweezers. Additionally, it is shown how further modification of the field configuration can yield a transverse field with a magnitude intermediate between that of the &#8220;conventional&#8221; magnetic tweezers and the freely-orbiting magnetic tweezers, which makes it possible to directly measure the torque stored in a biological molecule. This configuration is termed the magnetic torque tweezers. The accompanying video explains in detail how the conversion of conventional magnetic tweezers into freely-orbiting magnetic tweezers and magnetic torque tweezers can be accomplished, and demonstrates the use of these techniques. These adaptations maintain all the strengths of conventional magnetic tweezers while greatly expanding the versatility of this powerful instrument.

Magnetic tweezers, a powerful single-molecule manipulation technique, can be adapted for the direct measurements of the twist (using a configuration called freely-orbiting magnetic tweezers) and torque (using a configuration termed magnetic torque tweezers) in biological macromolecules. Guidelines for performing such measurements are given, including applications to the study of DNA and associated nucleo-protein filaments.

الملقط المغناطيسي لقياس تطور وعزم الدوران

Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques ...

High-resolution Spatiotemporal Analysis of Receptor Dynamics by Single-molecule Fluorescence Microscopy

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., kinetics, coexistence of different states and populations, transient interactions), which are typically hidden in ensemble measurements, such as those obtained with standard biochemical or microscopy methods. Thus, dynamic events, such as receptor-receptor interactions, can be followed in real time in a living cell with high spatiotemporal resolution. This protocol describes a method based on labeling with small and bright organic fluorophores and total internal reflection fluorescence (TIRF) microscopy to directly visualize single receptors on the surface of living cells. This approach allows one to precisely localize receptors, measure the size of receptor complexes, and capture dynamic events such as transient receptor-receptor interactions. The protocol provides a detailed description of how to perform a single-molecule experiment, including sample preparation, image acquisition and image analysis. As an example, the application of this method to analyze two G-protein-coupled receptors, i.e., &#946;2-adrenergic and &#947;-aminobutyric acid type B (GABAB) receptor, is reported. The protocol can be adapted to other membrane proteins and different cell models, transfection methods and labeling strategies.

This protocol describes how to use total internal reflection fluorescence microscopy to visualize and track single receptors on the surface of living cells and thereby analyze receptor lateral mobility, size of receptor complexes as well as to visualize transient receptor-receptor interactions. This protocol can be extended to other membrane proteins.

عالية الدقة تحليل الزمانية المكانية من مستقبلات حيوية من قبل جزيء واحدة الإسفار الميكروسكوب

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., ...

Single Molecule Fluorescence Microscopy on Planar Supported Bilayers

In the course of a single decade single molecule microscopy has changed from being a secluded domain shared merely by physicists with a strong background in optics and laser physics to a discipline that is now enjoying vivid attention by life-scientists of all venues 1. This is because single molecule imaging has the unique potential to reveal protein behavior in situ in living cells and uncover cellular organization with unprecedented resolution below the diffraction limit of visible light 2. Glass-supported planar lipid bilayers (SLBs) are a powerful tool to bring cells otherwise growing in suspension in close enough proximity to the glass slide so that they can be readily imaged in noise-reduced Total Internal Reflection illumination mode 3,4. They are very useful to study the protein dynamics in plasma membrane-associated events as diverse as cell-cell contact formation, endocytosis, exocytosis and immune recognition. Simple procedures are presented how to generate highly mobile protein-functionalized SLBs in a reproducible manner, how to determine protein mobility within and how to measure protein densities with the use of single molecule detection. It is shown how to construct a cost-efficient single molecule microscopy system with TIRF illumination capabilities and how to operate it in the experiment.

Preparation of protein-functionalized planar glass-supported lipid bilayers, determination of protein mobility within and measurement of protein densities is shown here. A roadmap to building a noise-reduced Total Internal Reflection microscope is outlined, which allows visualizing single bilayer-resident fluorochromes with high spatiotemporal resolution.

واحدة جزيء مضان المجهر على مستو المعتمدة طبقات ثنائية

In the course of a single decade single molecule microscopy has changed from being a secluded domain shared merely by physicists with a strong background ...

Label-free Single Molecule Detection Using Microtoroid Optical Resonators

Detecting small concentrations of molecules down to the single molecule limit has impact on areas such as early detection of disease, and fundamental studies on the behavior of molecules. Single molecule detection techniques commonly utilize labels such as fluorescent tags or quantum dots, however, labels are not always available, increase cost and complexity, and can perturb the events being studied. Optical resonators have emerged as a promising means to detect single molecules without the use of labels. Currently the smallest particle detected by a non-plasmonically-enhanced bare optical resonator system in solution is a 25 nm polystyrene sphere1. We have developed a technique known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that can surpass this limit and achieve label-free single molecule detection in aqueous solution2. As signal strength scales with particle volume, our work represents a &#62; 100x improvement in the signal to noise ratio (SNR) over the current state of the art. Here the procedures behind FLOWER are presented in an effort to increase its usage in the field.

We have developed a label-free biosensing system based on optical resonator technology known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that is capable of detecting single molecules in solution. Here the procedures behind this work are described and presented.

تسمية خالية واحدة كشف الجزيئة عن طريق Microtoroid البصرية الرنين

Detecting small concentrations of molecules down to the single molecule limit has impact on areas such as early detection of disease, and fundamental ...

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan electron-paramagnetic-resonance (RS-EPR), which can provide quantitative information under in vivo conditions on oxygen concentration, pH, redox status and concentration of signaling molecules (i.e., OH&#8226;, NO&#8226;). The RS-EPR technique has a higher sensitivity, improved spatial resolution (1 mm), and shorter acquisition time in comparison to the standard continuous wave (CW) technique. A variety of phantom configurations have been tested, with spatial resolution varying from 1 to 6 mm, and spectral width of the reporter molecules ranging from 16 &#181;T (160 mG) to 5 mT (50 G). A cross-loop bimodal resonator decouples excitation and detection, reducing the noise, while the rapid scan effect allows more power to be input to the spin system before saturation, increasing the EPR signal. This leads to a substantially higher signal-to-noise ratio than in conventional CW EPR experiments.

Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

A new electron paramagnetic resonance (EPR) method, rapid scan EPR (RS-EPR), is demonstrated for 2D spectral spatial imaging which is superior to the traditional continuous wave (CW) technique and opens new venues for in vivo imaging. Results are demonstrated at 250 MHz, but the technique is applicable at any frequency.

سرعة المسح الضوئي الكترون ممغطس الرنين تفتح آفاقا جديدة للالتصوير الناحية الفسيولوجية معلمات هام<em&gt; في فيفو</em

We demonstrate a superior method of 2D spectral-spatial imaging of stable radical reporter molecules at 250 MHz using rapid-scan ...

Fabrication of a Multiplexed Artificial Cellular MicroEnvironment Array

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are well orchestrated and are crucial in regulating cell functions in a living system. Although a number of researchers have attempted to investigate the correlation between environmental factors and desired cellular functions, much remains unknown. This is largely due to the lack of a proper methodology to mimic such environmental cues in vitro, and simultaneously test different environmental cues on cells. Here, we report an integrated platform of microfluidic channels and a nanofiber array, followed by high-content single-cell analysis, to examine stem cell phenotypes altered by distinct environmental factors. To demonstrate the application of this platform, this study focuses on the phenotypes of self-renewing human pluripotent stem cells (hPSCs). Here, we present the preparation procedures for a nanofiber array and the microfluidic structure in the fabrication of a Multiplexed Artificial Cellular MicroEnvironment (MACME) array. Moreover, overall steps of the single-cell profiling, cell staining with multiple fluorescent markers, multiple fluorescence imaging, and statistical analyses, are described.

This article describes the detailed methodology to prepare a Multiplexed Artificial Cellular MicroEnvironment (MACME) array for high-throughput manipulation of physical and chemical cues mimicking in vivo cellular microenvironments and to identify the optimal cellular environment for human pluripotent stem cells (hPSCs) with single-cell profiling.

تصنيع صفيف متعدد المكروية الخلوية اصطناعية

Cellular microenvironments consist of a variety of cues, such as growth factors, extracellular matrices, and intercellular interactions. These cues are ...

Characterizing Single-Molecule Conformational Changes Under Shear Flow with Fluorescence Microscopy

Single-molecule behavior under mechanical perturbation has been characterized widely to understand many biological processes. However, methods such as atomic force microscopy have limited temporal resolution, while F&#246;rster resonance energy transfer (FRET) only allow conformations to be inferred. Fluorescence microscopy, on the other hand, allows real-time in situ visualization of single molecules in various flow conditions. Our protocol describes the steps to capture conformational changes of single biomolecules under different shear flow environments using fluorescence microscopy. The shear flow is created inside microfluidic channels and controlled by a syringe pump. As demonstrations of the method, von Willebrand factor (VWF) and lambda DNA are labeled with biotin and fluorophore and then immobilized on the channel surface. Their conformations are continuously monitored under variable shear flow using total internal reflection (TIRF) and confocal fluorescence microscopy. The reversible unraveling dynamics of VWF are useful for understanding how its function is regulated in human blood, while the conformation of lambda DNA offers insights into the biophysics of macromolecules. The protocol can also be widely applied to study the behavior of polymers, especially biopolymers, in varying flow conditions and to investigate the rheology of complex fluids.

We present a protocol for immobilizing single macromolecules in microfluidic devices and quantifying changes in their conformations under shear flow. This protocol is useful for characterizing the biomechanical and functional properties of biomolecules such as proteins and DNA in a flow environment.

توصيف التغيرات التشكيلية أحادية الجزيء تحت تدفق القص مع المجهر الفلوري

Single-molecule behavior under mechanical perturbation has been characterized widely to understand many biological processes. However, methods such as ...