Simultaneous surface acoustic wave and surface plasmon resonance measurements: electrodeposition and biological interactions monitoring

We present results from an instrument combining surface acoustic wave (SAW) propagation and surface plasmon resonance (SPR) measurements. The objective is to use two independent methods, the former based on adsorbed mass change measurements and the latter on surface dielectric properties variations, to identify physical properties of protein layers, and more specifically their water content. We display mass sensitivity calibration curves using electrodeposition of copper leading to a sensitivity in liquid of 150$\pm15$ $cm^2/g$ for the Love mode device used here, and the application to monitoring biological processes. The extraction of protein layer thickness and protein to water content ratio is also presented for S-layer proteins under investigation. We obtain respectively 4.7$\pm$0.7 nm and 75$\pm$15%.Comment: 13 pages, 4 figure

Nanorheology of viscoelastic shells: Applications to viral capsids

We study the microrheology of nanoparticle shells [Dinsmore et al. Science 298, 1006 (2002)] and viral capsids [Ivanovska et al. PNAS 101, 7600 (2004)] by computing the mechanical response function and thermal fluctuation spectrum of a viscoelastic spherical shell that is permeable to the surrounding solvent. We determine analytically the damped dynamics of the shear, bend, and compression modes of the shell coupled to the solvent both inside and outside the sphere in the zero Reynolds number limit. We identify fundamental length and time scales in the system, and compute the thermal correlation function of displacements of antipodal points on the sphere and the mechanical response to pinching forces applied at these points. We describe how such a frequency-dependent antipodal correlation and/or response function, which should be measurable in new AFM-based microrheology experiments, can probe the viscoelasticity of these synthetic and biological shells constructed of nanoparticles.Comment: 17 page

Adjustable Ellipsoid Nanoparticles Assembled from Re-engineered Connectors of the Bacteriophage Phi29 DNA Packaging Motor

A 24 x 30 nm ellipsoid nanoparticle containing 84 subunits or 7 dodecamers of the re-engineered core protein of the bacteriophage phi29 DNA packaging motor was constructed. Homogeneous nanoparticles were obtained with simple one-step purification. Electron microscopy and analytical ultracentrifugation were employed to elucidate the structure, shape, size, and mechanism of assembly. The formation of this structure was mediated and stabilized by N-terminal peptide extensions. Reversal of the 84-subunit ellipsoid nanoparticle to its dodecamer subunit was controlled by the cleavage of the extended N-terminal peptide with a protease. The 84 outward-oriented C-termini were conjugated with a streptavidin binding peptide which can be used for the incorporation of markers. This further extends the application of this nanoparticle to pathogen detection and disease diagnosis by signal enhancement

Fabrication of Massive Sheets of Single Layer Patterned Arrays Using Lipid Directed Reengineered Phi29 Motor Dodecamer

The bottom-up assembly of patterned arrays is an exciting and important area in current nanotechnology. Arrays can be engineered to serve as components in chips for a virtually inexhaustible list of applications ranging from disease diagnosis to ultra-high-density data storage. Phi29 motor dodecamer has been reported to form elegant multilayer tetragonal arrays. However, multilayer protein arrays are of limited use for nanotechnological applications which demand nanoreplica or coating technologies. The ability to produce a single layer array of biological structures with high replication fidelity represents a significant advance in the area of nanomimetics. In this paper, we report on the assembly of single layer sheets of reengineered phi29 motor dodecamer. A thin lipid monolayer was used to direct the assembly of massive sheets of single layer patterned arrays of the reengineered motor dodecamer. Uniform, clean and highly ordered arrays were constructed as shown by both transmission electron microscopy and atomic force microscopy imaging

HERSTELLUNG ISOPORER ULTRAFILTRATIONSMEMBRANEN AUS KRISTALLINEN BAKTERIENZELLWANDSCHICHTEN

Viele Eu- und Archaebakterien besitzen eine kristalline Protein- oder Glykoproteinschicht (S-Schicht) als äußerste Zellgrenzfläche. Über | eine Reihe einfacher Verfahrensschritte ist es möglich, S-Schichten | zu isolieren und an geeignete poröse Träger zu binden. Auf diese Weise kann ein völlig neuartiger Typ von Ultrafiltrationsmembranen hergestellt werden, dessen aktive Trennschicht sich durch absolute Isoporosität auszeichnet und über ein breites Spektrum proteinchemischer Reaktionen spezifisch modifiziert werden kann

Relevance of charged groups for the integrity of the S-layer from Bacillus coagulans E38-66 and for molecular interactions.

In this paper, the importance of charged amino and carboxyl groups for the integrity of the cell surface layer (S-layer) lattice from Bacillus coagulans E38-66 and for the self-assembly of the isolated subunits was investigated. Amidination of the free amino groups which preserved their positive net charge had no influence on both. On the other hand, acetylation and succinylation, which converted the amino groups into either neutral or negatively charged groups, and amidation of carboxyl groups were accompanied by the disintegration or at least by the loss of the regular structure of the S-layer lattice. Treatment of S-layer monolayers with the zero-length cross-linker carbodiimide led to the introduction of peptide bonds between activated carboxyl groups and amino groups from adjacent subunits. This clearly indicated that in the native S-layer lattice the charged groups are located closely enough for direct electrostatic interactions. Under disrupting conditions in which the S-layer polypeptide chains were unfolded, 58% of the Asx and Glx residues could be amidated, indicating that they occur in the free carboxylic acid form. As derived from chemical modification of monolayer self-assembly products, about 90% of the lysine and 70% of the aspartic and glutamic acid residues are aligned on the surface of the S-layer protein domains. This corresponded to 45 amino groups and to 63 carboxyl groups per S-layer subunit. Labelling experiments with macromolecules with different sizes and charges and adsorption studies with ion-exchange particles revealed a surplus of free carboxyl groups on the inner and on the outer faces of the S-layer lattice. Since the carboxyl groups on the outer S-layer face were accessible only for protein molecules significantly smaller then the S-layer protomers or for positively charged, thin polymer chains extending from the surface of ion-exchange beads, the negatively charged sites must be located within indentations of the corrugated S-layer protein network. This was in contrast to the carboxyl groups on the inner S-layer face, which were found to be exposed on elevations of the S-layer protein domains (D. Pum, M. Sára, and U.B. Sleytr, J. Bacteriol. 171:5296-5303, 1989)