The present work was partially funded by the IGF-project &#34;S-Sieve&#34; (490 ZBG/1) funded by the BMWi and the BMBF-project &#34;Aptasens&#34; (BMBF/DLR 01RB0805A). Special thanks to Tobias J. G&#252;nther for his valuable help during AFM studies and to Erik V. Johnstone for reading the manuscript as a native English speaker. Further, the author of this paper would like to thank Aline Ritter and Sabrina Gurlit (from Institute for Resource Ecology for assistance in ICP-MS measurements), Manja Vogel, Nancy Unger, Karen E. Viacava and the group biotechnology of the Helmholtz-Institute Freiberg for Resource Technology.

1. Microorganism and Cultivation Conditions
Note: All experiments were done under sterile conditions. L. sphaericus JG-B53 was obtained from a cryo-preserved culture 29,30.
<ol>
	<li>Transfer cryo-preserved culture (1.5 ml) under the clean bench to 300 ml sterile nutrient broth (NB) media (3 g/L meat extract, 5 g/L peptone, 10 g/L NaCl). Afterwards stir the solution for at least 6 hr at 30 &#176;C to obtain the pre-culture for cultivation.</li>
	<li>Cultivate the bacteria u...

The authors have nothing to disclose.

In this work studied the binding of Au to S-layer proteins was investigated using a combination of different analytical methods. In particular, the binding of Au is very attractive not only for the recovery of Au from mining waters or process solutions, but also for the construction of materials, e.g., sensory surfaces. For studies of the Au interaction (Au(III) and Au(0)-NPs) with suspended and recrystallized monolayer of Slp1, the protein had to be isolated. Therefore, this study has shown the successful culti...

Due to the increasing use of gold for several applications like electronics, catalysts, biosensors, or medical instruments, the demand of this precious metal has grown over the last few years&#39; time 6-9. Gold as well as many other precious and heavy metals are released into the environment via industrial effluents in dilute concentrations, through mining activities, and waste disposal 7,8,10,although most environmental contamination by heavy or precious metals is an on-going process mainly caused by technological activities. This leads to a significant interference of natural ecosystems and could potentially threaten human health 9. Knowing these negative outcomes promotes the search for new techniques to remove metals from contaminated ecosystems and improvements in recycling metals from industrial wastewater. Well-established physico-chemical methods like precipitation or ion exchange are not so effective, especially in highly diluted solutions 7,8,11. Biosorption, either with living or dead biomass, is an attractive alternative for wastewater treatment 10,12. The use of such biological materials can reduce the consumption of toxic chemicals. Many microorganisms have been described to accumulate or immobilize metals. For instance, cells of Lysinibacillus sphaericus (L. sphaericus) JG-A12 have shown high binding capacities for precious metals, e.g., Pd(II), Pt(II), Au (III), and other toxic metals like Pb(II) or U(VI) 4,13, cells of Bacillus megaterium for Cr(VI) 14, cells of Saccharomyces cerevisiae for Pt(II) and Pd(II) 15, and Chlorella vulgar for Au(III) and U(VI) 16,17. The binding of previous metals like Au(III), Pd(II), and Pt(II) has also been reported for Desulfovibrio desulfuricans18 and for L. sphaericus JG-B53 19,20. Nevertheless, not all microbes bind high amounts of metals and their application as sorptive material is limited 12,21. Furthermore, metal binding capacity depends on different parameters, e.g., cell composition, the used bio-component, or environmental and experimental conditions (pH, ionic strength, temperature etc.). The study of isolated cell wall fragments 22,23, like membrane lipids, peptidoglycan, proteins, or other components, helps to understand the metal binding processes of complex constructed whole cells 8,21.
The cell components focused on in this study are S-layer proteins. S-layer proteins are parts of the outer cell envelope of many bacteria and archaea, and they constitute about 15 - 20% of the total protein mass of these organisms. As the first interface to the environment, these cell compounds strongly influence the bacterial sorption properties 3. S-layer proteins with molecular weights ranging from forty to hundreds of kDa are produced within the cell, but are assembled outside where they are able to form layers on the lipid membranes or polymeric cell wall components. Once isolated, nearly all S-layer proteins have the intrinsic property to spontaneously self-assemble in suspension, at interfaces, or on surfaces forming planar or tube-like structures 3. The thickness of the protein monolayer depends on the bacteria and is within a range of 5 - 25 nm 24. In general, the formed S-layer protein structures can have an oblique (p1 or p2), square (p4), or hexagonal (p3 or p6) symmetry with lattice constants of 2.5 to 35 nm 3,24. The lattice formation seems to be in many cases dependent on divalent cations and mainly on Ca2+ 25,26, Raff, J. et al. S-layer based nanocomposites for industrial applications in Protein-based Engineered Nanostructures. (eds Tijana Z. Grove &#38; Aitziber L. Cortajarena) (Springer, 2016 (submitted)). Nevertheless, the full reaction cascade of monomer folding, monomer-monomer interaction, the formation of a lattice, and the role of different metals, especially of divalent cations such as Ca2+ and Mg2+, are still not fully understood.
The gram-positive strain L. sphaericus JG-B53 (renamed from Bacillus sphaericus after new phylogenetic classification) 27 was isolated from the uranium mining waste pile &#34;Haberland&#34; (Johanngeorgenstadt, Saxony, Germany) 4,28,29. Its functional S-layer protein (Slp1) possesses a square lattice, a molecular weight of 116 kDa 30, and a thickness of &#8776; 10 nm on living bacteria cells 31. In previous studies, the in vitro formation of a closed and stable protein layer with a thickness of approximately 10 nm was achieved in less than 10 min&#160;19. The related strain L. sphaericus JG-A12, also an isolate from the &#34;Haberland&#34; pile, possesses high metal binding capacities and its isolated S-layer protein has shown a high chemical and mechanical stability and good sorption rates for precious metals like Au(III), Pt(II), and Pd(II) 4,32,33. This binding of precious metals is more or less specific for some metals and depends on the availability of functional groups on the outer and inner protein surface of the polymer and in its pores, ionic strength, and the pH value. Relevant functional groups for metal interaction by the proteins are COOH-, NH2-, OH-, PO4-, SO4-, and SO-. In principle, metal binding capacities open a wide spectrum of applications,Raff, J. et al. S-layer based nanocomposites for industrial applications in Protein-based Engineered Nanostructures. (eds Tijana Z. Grove &#38; Aitziber L. Cortajarena) (Springer, 2016 (submitted)).e.g., as biosorptive components for removal or recovery of dissolved toxic or valuable metals, templates for synthesis or defined deposition of regularly structured metallic nanoparticles (NPs) for catalysis, and other bio-engineered materials like bio-sensory layers 3,5,18,33. Regularly arranged NP arrays like Au(0)-NPs could be used for major applications ranging from molecular electronics and biosensors, ultrahigh density storage devices, and catalysts for CO-oxidation 34-37. The development of such applications and smart design of these materials necessitates a deeper understanding of the underlying metal binding mechanisms.
A prerequisite for the development of such bio-based materials is the reliable implementation of an interface layer between the biomolecule and the technical surface 38,39. For example, polyelectrolytes assembled with the layer-by-layer (LbL) technique 40,41 have been used as an interface layer for recrystallization of S-layer proteins 39. Such an interface offers a relatively easy way to perform the protein coating in a reproducible and quantitative way. By performing different experiments with and without modification with adhesive promoters, it is possible to make statements regarding coating kinetics, layer stability, and interaction of metals with biomolecules 19,42,Raff, J. et al. S-layer based nanocomposites for industrial applications in Protein-based Engineered Nanostructures. (eds Tijana Z. Grove &#38; Aitziber L. Cortajarena) (Springer, 2016 (submitted)). However, the complex mechanism of the protein adsorption and protein-surface interaction is not completely understood. Especially information on conformation, pattern orientation, and coating densities is still missing.
Quartz crystal microbalance with dissipation monitoring (QCM-D) technique has attracted attention in the recent years as a tool for studying protein adsorption, coating kinetics, and interaction processes on the nanometer scale 19,43-45. This technique allows for the detailed detection of mass adsorption in real-time, and can be used as an indicator for the protein self-assembling process and coupling of functional molecules on protein lattices 19,20,42,46-48. In addition, QCM-D measurements open the possibility to study metal interaction processes with the proteinaceous layer under natural biological conditions. In a recent study, the interaction of the S-layer protein with selected metals like Eu(III), Au(III), Pd(II),and Pt(II) has been studied with QCM-D 19,20. The adsorbed protein layer can serve as a simplified model of a cell wall of gram-positive bacteria. The study of this single component can contribute to a deeper understanding of metal interaction. However, solely QCM-D experiments do not allow statements regarding surface structures and influences of metals to protein. Other techniques are necessary to obtain such information. One possibility for imaging bio-nanostructures and obtaining information on structural properties is the atomic force microscopy (AFM).
The objective of the presented study was to investigate the sorption of gold (Au(III) and Au(0)-NPs) to S-layer proteins, in particular Slp1 of L. sphaericus JG-B53. Experiments were done with suspended proteins on batch scale in a pH range of 2.0 - 5.0 using ICP-MS and with immobilized S-layers using QCM-D. Additionally, the influence of metal salt solution on the lattice stability was investigated with subsequent AFM studies. The combination of these techniques contributes to a better understanding of in vitro metal interaction processes as a tool for learning more about binding events on whole bacterial cells regarding specific metal affinities. This knowledge is not only crucial for the development of applicable filter materials for the recovery of metals for environmental protection and the conservation of resources 49, but also for the development of arrays of highly ordered metallic NPs for various technical applications.

<table border="0" cellpadding="0" cellspacing="0" width="849">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">equiment and software</td>
			<td style="width:219px;"></td>
			<td style="width:97px;"></td>
			<td style="width:241px;"></td>
		</tr>
		<tr height="36">
			<td height="36" style="height:36px;width:293px;">Bioreactor, Steam In Place 70L Pilot System</td>
			<td style="width:219px;">Applikon Biotechnology, Netherlands</td>
			<td style="width:97px;">Z6X</td>
			<td style="width:241px;">Including dO2, pH sensors of Applikon Biotechnology and BioXpert software V2</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Noninvasive Biomass Monitor BugEye 2100</td>
			<td style="width:219px;">BugLab, Concord (CA), USA</td>
			<td style="width:97px;">Z9X</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Spectrometer Ultrospec 1000</td>
			<td style="width:219px;">Amersham Pharmacia Biotech, Great Britain</td>
			<td style="width:97px;">80-2109-10</td>
			<td style="width:241px;">Company now GE Healthcare Life Sciences</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">MiniStar micro centrifuge</td>
			<td style="width:219px;">VWR, Germany</td>
			<td style="width:97px;">521-2844</td>
			<td style="width:241px;">For centrifugation of cultivation samples</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Research system microscope BX-61</td>
			<td style="width:219px;">Olympus Germany LLC, Germany</td>
			<td style="width:97px;">037006</td>
			<td style="width:241px;">Microscope in combination with imaging software</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Cell^P (version 3.1)</td>
			<td style="width:219px;">Olympus Soft Imaging Solutions LLC, M&#252;nster, Germany</td>
			<td style="width:97px;">---</td>
			<td style="width:241px;">together with microscope</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Powerfuge Pilot Separation System Serie 9010-S</td>
			<td style="width:219px;">Carr Centritech, Florida, USA</td>
			<td style="width:97px;">9010PLT</td>
			<td style="width:241px;">For biomasse harvesting</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">T18 basic Ultra Turrax</td>
			<td style="width:219px;">IKA Labortechnik, Germany</td>
			<td style="width:97px;">431-2601</td>
			<td style="width:241px;">For flagella removal and sample homogenization</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Sorvall Evolution RC Superspeed Centrifuge</td>
			<td style="width:219px;">Thermo Fisher Scientific, USA</td>
			<td style="width:97px;">728411</td>
			<td style="width:241px;">Used within protein isolation</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Mobile high shear fluid processor, M-110EH-30 Pilot</td>
			<td style="width:219px;">Microfluidics, Massachusetts, USA</td>
			<td style="width:97px;">M110EH30K</td>
			<td style="width:241px;">Used for cell rupture</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Alpha 1-4 LSC Freeze dryer</td>
			<td style="width:219px;">Martin Christ Freeze dryers LLC, Osterode, Germany</td>
			<td>102041</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">UV-VIS spectrophotometry (NanoDrop 2000c)</td>
			<td style="width:219px;">Thermo Fisher Scientific, USA</td>
			<td style="width:97px;">91-ND-2000C-L</td>
			<td style="width:241px;">For determination of protein concentration</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Mini-PROTEAN vertical electrophoresis chamber</td>
			<td style="width:219px;">Bio-Rad Laboratories GmbH, Munich, Germany</td>
			<td style="width:97px;">165-3322</td>
			<td style="width:241px;">For SDS-PAGE</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">VersaDoc Imaging System 3000</td>
			<td style="width:219px;">Bio-Rad Laboratories GmbH, Munich, Germany</td>
			<td style="width:97px;">1708030</td>
			<td style="width:241px;">Used for imaging of SDS-PAGE gels</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">ICP-MS Elan 9000</td>
			<td style="width:219px;">PerkinElmer, Waltham (MA), USA</td>
			<td style="width:97px;">N8120536</td>
			<td style="width:241px;">For determination of metal concentration</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Zetasizer Nano ZS</td>
			<td style="width:219px;">Malvern Instruments, Worcestershire United Kingdom</td>
			<td style="width:97px;">ZEN3600</td>
			<td style="width:241px;">For determination of nanoparticle size</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Q-Sense E4 device&#160;</td>
			<td style="width:219px;">Q-Sense AB, Gothenburg, Sweden</td>
			<td rowspan="3" style="width:97px;">QS-E4</td>
			<td rowspan="3" style="width:241px;">ordered via LOT quantum design (software included with E4 platform)</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Q-Soft 401 (data recording)</td>
			<td style="width:219px;">Q-Sense AB, Gothenburg, Sweden</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Q-Tools 3 (data evaluation and modelling)</td>
			<td style="width:219px;">Q-Sense AB, Gothenburg, Sweden</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">QCM-D flow modules QFM&#160;401&#160;</td>
			<td style="width:219px;">Q-Sense AB, Gothenburg, Sweden</td>
			<td style="width:97px;">QS-QFM401</td>
			<td style="width:241px;">ordered via LOT quantum design</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">QSX&#160;303 SiO2 piezoelectric AT-cut quartz sensors</td>
			<td style="width:219px;">Q-Sense AB, Gothenburg, Sweden</td>
			<td style="width:97px;">QS-QSX303</td>
			<td style="width:241px;">ordered via LOT quantum design</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Ozone cleaning chamber</td>
			<td style="width:219px;">Bioforce Nanoscience, Ames (IA), USA</td>
			<td style="width:97px;">QS-ESA006</td>
			<td style="width:241px;">ordered via LOT quantum design</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Atomic Force Microscope MFP-3D Bio AFM</td>
			<td style="width:219px;">Asylum Research, Santa Barbara (CA), USA</td>
			<td>MFP-3DBio</td>
			<td style="width:241px;">AFM measurements and imaging software</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Asylum Research AFM Software AR Version 120804+1223</td>
			<td style="width:219px;">Asylum Research, Santa Barbara (CA), USA</td>
			<td style="width:97px;">---</td>
			<td style="width:241px;">imaging software included in Cat. No. MFP-3DBio</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Igor Version Pro 6.3.2.3 Software</td>
			<td style="width:219px;">WaveMetrics, Inc., USA</td>
			<td style="width:97px;">---</td>
			<td style="width:241px;">imaging software included in Cat. No. MFP-3DBio</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">BioHeater</td>
			<td style="width:219px;">Asylum Research, Santa Barbara (CA), USA</td>
			<td style="width:97px;">Bioheater</td>
			<td style="width:241px;">Sample heater for AFM measurements</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Biolever mini cantilever,&#160; BL-AC40TS-C2</td>
			<td style="width:219px;">Olympus Germany LLC, Germany</td>
			<td style="width:97px;">&#160;BL-AC40TS-C2</td>
			<td style="width:241px;">Prefered cantilever for AFM measurements</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">WSxM 5.0 Develop 6.5 (2013)</td>
			<td style="width:219px;">Nanotec Electronica S.L. , Spain</td>
			<td style="width:97px;">freeware</td>
			<td style="width:241px;">Software for AFM analysis</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">Name</td>
			<td style="width:219px;">Company</td>
			<td style="width:97px;">Catalog Number</td>
			<td style="width:241px;">Comments</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">Detergents and other equiment</td>
			<td style="width:219px;"></td>
			<td style="width:97px;"></td>
			<td style="width:241px;"></td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">Calcium chloride Dihydrate (CaCl2 &#8729; 2H2O)</td>
			<td style="width:219px;">Merck KGaA</td>
			<td style="width:97px;">1.02382</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="51">
			<td height="51" style="height:51px;width:293px;">acidic acid, 100 %, p.A.</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">3738.5</td>
			<td style="width:241px;">Danger, flammable and corrosive liquid and vapour. Causes severe skin burns and eye damage.</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Antifoam 204</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">A6426</td>
			<td style="width:241px;">For foam suppression</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">bromophenol blue, sodium salt</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">B5525</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">Coomassie Brilliant Blue R (C45H44N3NaO7S2)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">3862.1</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Deoxyribonuclease II from porcine spleen</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">D4138</td>
			<td style="width:241px;">Typ IV , 2,000-6,000&#160;Kunitz units/mg protein</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Ethanol, 95%</td>
			<td style="width:219px;">VWR, Germany</td>
			<td style="width:97px;">20827.467</td>
			<td style="width:241px;">Danger, flammable</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">glycerine, p.A.</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">3783.1</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">Gold(III) chloride trihydrate (HAuCl4 &#8729; 3H2O)</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">520918</td>
			<td style="width:241px;">Danger</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Guanidine hydrochloride (GuHCl)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">0037.1</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Hellmanex III</td>
			<td style="width:219px;">Hellma GmbH &#38; Co. KG</td>
			<td style="width:97px;">9-307-011-4-507</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:293px;">Hydrochloric acid (HCl) (37%)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">4625.2</td>
			<td style="width:241px;">Danger; Corrosive, used for pH adjustment</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Lysozyme from chicken egg white</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">L6876&#160;</td>
			<td style="width:241px;">Lyophilized powder, protein =90 %, =40,000 units/mg protein (Sigma)&#160;</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">Magnesium chloride Hexahydrate (MgCl2 &#8729; 6H2O)</td>
			<td style="width:219px;">Merck KGaA</td>
			<td style="width:97px;">1.05833</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Magnetic stirrer with heating,&#160; MR 3000K</td>
			<td style="width:219px;">Heidolph Instruments GmbH &#38; Co.KG, Germany</td>
			<td style="width:97px;">504.10100.00</td>
			<td style="width:241px;">Standard stirrer within experiment</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">NB-Media DM180</td>
			<td style="width:219px;">Mast Diagnostica GmbH</td>
			<td style="width:97px;">121800</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">Nitric acid (HNO3)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">HN50.1</td>
			<td style="width:241px;">Danger; Oxidizing, Corrosing</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">PageRuler Unstained Protein Ladder</td>
			<td style="width:219px;">ThermoScientific-Pierce</td>
			<td style="width:97px;">26614</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Poly(sodium 4-styrenesulfonat) (PSS)</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">243051</td>
			<td style="width:241px;">Average Mw ~70,000</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Polyethylenimine (PEI), branched</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">408727</td>
			<td style="width:241px;">Warning; Harmful, Irritant, Dangerous for the environment; average Mw ~25,000</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:293px;">Potassium carbonate anhydrous (K2CO3)</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">60108</td>
			<td style="width:241px;">Warning; Harmful</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Ribonuclease A from bovine pancreas&#160;</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">R5503</td>
			<td style="width:241px;">Type I-AS, 50-100 Kunitz units/mg protein&#160;</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Sodium azide (NaN3)</td>
			<td style="width:219px;">Merck KGaA</td>
			<td style="width:97px;">106688</td>
			<td style="width:241px;">Danger; very toxic and Dangerous for the environment</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Sodium chloride (NaCl)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">3957.2</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Sodium dodecyl sulfate (SDS)</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">L-5750</td>
			<td style="width:241px;">Danger; toxic</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Sodium hydroxide (NaOH)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">6771.1</td>
			<td style="width:241px;">Danger; Corrosive, used for pH regulation within cultivation and pH adjustment</td>
		</tr>
		<tr height="17">
			<td height="17" style="height:17px;width:293px;">Spectra/Por 6, Dialysis membrane, MWCO 50,000&#160;</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">1893.1</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Sulfuric acid (H2SO4)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">HN52.2</td>
			<td style="width:241px;">Danger; Corrosive, used for pH regulation within cultivation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">Tannic acid (C76H52O46)</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">16201</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">TRIS HCl (C4H11NO3HCl)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">9090.2</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">Tri-sodium citrate dihydrate (C6H5Na3O7 &#8729; 2H2O)</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">3580.2</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="34">
			<td height="34" style="height:34px;width:293px;">Triton X-100</td>
			<td style="width:219px;">CARL ROTH GmbH+CO.KG</td>
			<td style="width:97px;">3051.3</td>
			<td style="width:241px;">Warning; Harmful, Dangerous for the environment</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">VIVASPIN 500, 50.000 MWCO Ultrafiltration tubes</td>
			<td>Sartorius AG</td>
			<td>VS0132</td>
			<td style="width:241px;">---</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:293px;">&#946;-mercaptoethanol</td>
			<td style="width:219px;">Sigma-Aldrich Co. LLC.</td>
			<td style="width:97px;">M6250</td>
			<td style="width:241px;">Danger, toxic</td>
		</tr>
	</tbody>
</table>

au-interaction of slp1 polymers and monolayer from lysinibacillus sphaericus jg-b53 - qcm-d, icp-ms and afm as tools for biomolecule-metal studies

In this publication the gold sorption behavior of surface layer (S-layer) proteins (Slp1) of Lysinibacillus sphaericus JG-B53 is described. These biomolecules arrange in paracrystalline two-dimensional arrays on surfaces, bind metals, and are thus interesting for several biotechnical applications, such as biosorptive materials for the removal or recovery of different elements from the environment and industrial processes. The deposition of Au(0) nanoparticles on S-layers, either by S-layer directed synthesis 1 or adsorption of nanoparticles, opens new possibilities for diverse sensory applications. Although numerous studies have described the biosorptive properties of S-layers 2-5, a deeper understanding of protein-protein and protein-metal interaction still remains challenging. In the following study, inductively coupled mass spectrometry (ICP-MS) was used for the detection of metal sorption by suspended S-layers. This was correlated to measurements of quartz crystal microbalance with dissipation monitoring (QCM-D), which allows the online detection of proteinaceous monolayer formation and metal deposition, and thus, a more detailed understanding on metal binding.
The ICP-MS results indicated that the binding of Au(III) to the suspended S-layer polymers is pH dependent. The maximum binding of Au(III) was obtained at pH 4.0. The QCM-D investigations enabled the detection of Au(III) sorption as well as the deposition of Au(0)-NPs in real-time during the in situ experiments. Further, this method allowed studying the influence of metal binding on the protein lattice stability of Slp1. Structural properties and protein layer stability could be visualized directly after QCM-D experiment using atomic force microscopy (AFM). In conclusion, the combination of these different methods provides a deeper understanding of metal binding by bacterial S-layer proteins in suspension or as monolayers on either bacterial cells or recrystallized surfaces.

Cultivation of Microorganisms and Slp1 Characterization
The recorded data of bacterial growth indicates the end of the exponential growth phase at around 5 hr. Previous investigations have shown that Slp1 can be isolated from this point of harvest (4.36 g/L wet biomass (&#8776; 1.45 g/L (BDW)) with a maximum yield 19. Nevertheless, optimization of cultivation by using defined media components or fed-b...

Watch this Scientific Journal Video about Au-Interaction of Slp1 Polymers and Monolayer from Lysinibacillus sphaericus JG-B53 - QCM-D, ICP-MS and AFM as Tools for Biomolecule-metal Studies at JoVE.com

Au-Interaction of Slp1 Polymers and Monolayer from Lysinibacillus sphaericus JG-B53 - QCM-D, ICP-MS and AFM as Tools for Biomolecule-metal Studies

To obtain basic information on the sorption and recycling of gold from aqueous systems the interaction of Au(III) and Au(0) nanoparticles on S-layer proteins were investigated. The sorption of protein polymers was investigated by ICP-MS and that of proteinaceous monolayers by QCM-D. Subsequent AFM enables the imaging of the nanostructures.

Au-Interaction of Slp1 Polymers and Monolayer from Lysinibacillus sphaericus JG-B53 - QCM-D, ICP-MS and AFM as Tools for Biomolecule-metal Studies

In this publication the gold sorption behavior of surface layer (S-layer) proteins (Slp1) of Lysinibacillus sphaericus JG-B53 is described. These ...

The overall goal of this experiment is to investigate the gold sorption behavior by S-layer proteins of the presented bacterial strain from an ecological and technological point of view. These methods can answer key question in environmental related science at such is fields of sorption processes and removal and recovery of metals. The main advantage of these techniques are that you can detect metal sorption and nanoparticle adsorption in another scale range.By using QCM-D it is possible to detect this in an real-time measurement. To begin this procedure, equip the fluid cells with sensor dummies. Pump at least 20 milliliters per module of a 2%alkaline liquid cleansing agent in ultrapure water through the QCM-D and tube system.Following this, pump a five-fold volume per module of ultrapure water through the system with a flow rate up to 300 microliters per minute per the manufacturer's protocol. Clean the silicon dioxide sensors outside the flow modules by incubation in 2%sodium dodecyl sulfate solution for at least 20 minutes. Then, rinse the sensors several times with ultrapure water.After drying the crystals with filtered compressed air, place them in an ozone cleaning chamber for 20 minutes. Following this, repeat the cleaning procedure twice to remove all organic contents. To remove bound metals from the sensor surface, rinse the sensors with one molar nitric acid.Then rinse the sensors several times with ultrapure water. Next, modify the sensors with three grams per liter of alternating layers of polyethylenimine and polystyrene sulfonate via dip coating using the layer by layer or LBL technique. Place the sensors inside the appropriate polyelectrolyte solution in deep-well plates and incubate these for 10 minutes at room temperature.Then, remove the sensors from the polyelectrolyte solution and rinse them between every dip coating step intensively with ultrapure water. Once the external modification is complete, place the sensors inside the flow module. Equilibrate the sensors by rinsing them with ultrapure water before starting the experiments.At this point, dissolve previously isolated and purifed Slp1 in formula urea for converting the polymers into monomers. Centrifuge the monomerized proteins at 15, 000 times g and 4 degrees Celsius for one hour to remove bigger protein agglomerates. Mix the solubilized and centrifuged Slp1 supernatant with recrystallization buffer to a final protein concentration of 0.2 grams per liter.After successful protein recrystallization on top of the polyelectrolyte modified sensors inside the flow modules, rinse the coated sensors with recrystallization buffer intensively with a flow rate of 125 microliters per minute until stable values of frequency and dissipation shifts are detected. After successful Slp1 coating in the flow modules, rinse the obtained Slp1 layer intensively with 1.6 millimolar citrate buffer pH 5.0 until stable values of frequency and dissipation shifts are detected. Next, pump a previously prepared one millimolar nanoparticle solution to the flow modules with a flow rate of 125 microliters per minute.Then, track the mass adsorption to the Slp1 layer. After completing the metal nanoparticle interaction rinse the layer with nanoparticle-free buffer to remove weak bound metals or nanoparticles. Using an atomic force microscope or AFM with an inverted optical microscope, record images in liquid using ultrapure water directly on the coated QCM-D sensors.Rinse the sensors with ultrapure water after the QCM-D experiments and place them inside the AFM fluid cell. Use a cantilever with a resonance frequency of approximately 25 kilohertz in water and a stiffness of less than 0.1 newton per meter. Adjust the scanning speed between 2.5 and 10 micrometers per second.Take images in dynamic contact mode while the cantilever is excited by a Piezo at its resonance frequency. Finally, determine the distance of the cantilever to the surface by the oscillation damping. The maximum metal binding capacities of gold three by suspended Slp1 show that it was stabily bound during the 24-hour incubation within the investigated pH range.The immediate decrease in frequency indicates a rapid adsorption and a high affinity of the proteins to the polyelectrolyte modified surface. The dissipation also increases immediately which indicates an adsorption of viscoelastic molecules to the surface because of fast damping resulting in increasing dissipation values. Presynthesized gold zero nanoparticles were incubated with Slp1 and analyzed by SDS-PAGE which verified the QCM-D data showing that nanoparticles do not disturb the Slp1 structure.The adsorption of presynthesized metallic gold zero nanoparticles is shown for QCM-D experiments in delta F-delta D plots and as thickness and mass profiles. The protein lattice of Slp1 recrystallized on polyelectrolyte modified sensors is shown here. The lattice constant was determined as 13 to 14 nanometers and the layer thickness was found to be 10 plus or minus two nanometers.AFM studies verified that after the gold three interaction the Slp1 lattice remained completely intact which confirms the QCM-D results that predicted the stability of the coating. AFM verifies the adsorption of gold zero nanoparticles on the Slp1 lattice but due to the particle size, they do not follow the p4 symmetry of Slp1. Once mastered this technique can be done within one working day if it is performed properly.Following these methods, other techniques like infrared spectroscopy or helium ion microscopy can be performed to answer further questions like specific binding sights or interaction with gold or gold nanoparticles. The presented technique paved the way for the uzrachem to study the interactions of biomolecules with metals and for example the adsorption and disorption behavior on different kind of surfaces. After watching this video, you should now have a good understanding of how to investigate interactions of metals with biological solventses and please when you are using this method don't forget to use goggles, lab coat and of course also gloves.

au-interaction-slp1-polymers-monolayer-from-lysinibacillus-sphaericus

Research

JoVE Journal

Chemistry

11.3K visualizações.  Helmholtz-Zentrum Dresden-Rossendorf. The overall goal of this experiment is to investigate the gold sorption behavior by S-layer proteins of the presented bacterial strain from an ecological and technological point of view. These methods can answer key question in environmental related science at such is fields of sorption processes and removal and recovery of metals. The main advantage of these techniques are that you can detect metal sorption and nanoparticle adsorption in another scale range.By using QCM-D it is possib...

Vídeo: Au-Interaction of Slp1 Polymers and Monolayer from Lysinibacillus sphaericus JG-B53 - QCM-D, ICP-MS and AFM as Tools for Biomolecule-metal Studies