Scanning Probe Microscopy of Bacterial Red Light Photoreceptors

2012 ◽  
Vol 1465 ◽  
Author(s):  
Fernando G. Tobias ◽  
Anna Gawedzka ◽  
Max S. Goldmeier ◽  
Alexandra C. Sakols ◽  
Emina A. Stojković ◽  
...  
Keyword(s):  
Scanning Probe Microscopy ◽  
Structural Changes ◽  
Structural Model ◽  
Fluorescent Protein ◽  
Red Light ◽  
Hexagonal Lattice ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Probe Microscopy ◽  
Insight Into

ABSTRACTBacteriophytochromes (Bphs) are red-light photoreceptors found in photosynthetic and non-photosynthetic bacteria that have been engineered into infrared fluorescent protein markers. Bphs are composed of a photosensory module that is covalently linked to an effector/regulatory module, usually a histidine kinase (HK) domain. Light-induced, global structural changes are proposed to originate within the covalently attached biliverdin chromophore, a linear tetrapyrrole, and propagate through the protein. Bphs undergo reversible photoconversion between two distinct red and far-red light absorbing states, denoted Pr and Pfr respectively. For most Bphs, Pr is the dark-adapted state. The energy dissipated during Pr/Pfr photoconversion is proposed to directly impact the infrared fluorescence quantum yield. At this time, only structures of three different Bphs have been published, all of truncated proteins in their respective dark-adapted states. We have utilized scanning probe microscopy (SPM) to investigate the structure of intact Bphs in the light-adapted state in order to gain new insight into the mechanism of photoconversion and fluorescence. Scanning tunneling microscopy (STM) analysis of a pair of Bphs from photosynthetic bacterium R. palustris, RpBphP2 (P2) and RpBphP3 (P3) in their light-adapted states is presented in these proceedings. The concentration of the depositing protein has a key role in the molecular arrangements observed on the highly-ordered pyrolytic graphite (HOPG) surface. For example, at a high protein concentration, a hexagonal lattice of Bphs is observed by STM on a HOPG surface. Upon dilution, the photoreceptors self-organize into fiber-like structures on the surface. In these fibers, the dimer interface and the individual domains of the Bphs can be assigned and directly compared to a structural model of the intact, full-length proteins. In summary, SPM has potential to be an effective method for gaining new insight into Bph structure and dynamics.

Recognition, Specificity, Scanning Probe Microscopy and Biomaterials

2001 ◽  
Vol 7 (S2) ◽  
pp. 130-131
Author(s):  
Buddy D. Ratner ◽  
Reto Luginbühll ◽  
Rene Overney ◽  
Michael Garrison ◽  
Thomas Boland
Keyword(s):  
Scanning Probe Microscopy ◽  
Secondary Ion Mass Spectrometry ◽  
Film Structure ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Specific Information ◽  
Tunneling Microscopy ◽  
Probe Microscopy ◽  
Biomaterial Surfaces ◽  
Nucleotide Bases

Although scanning probe microscopy (SPM) can generate images of surface topography, this class of techniques is exceptionally valuable in its ability to provide quantitative and chemically specific information about biomaterial surfaces with high spatial definition. Since engineered biomaterials are designed to deliver chemically defined information, often arrayed in specific geometries, tools that can characterize such materials are needed.A few years ago, we demonstrated how the atomic force microscope (AFM) could precisely distinguish between each of the four nucleotide bases that comprise DNA, measure the nucleotide-nucleotide force of interaction and spatially localize that information on a surface (1). in particular, we found that the nucleotide bases could self-assemble on gold. The assembly process was imaged using scanning tunneling microscopy (STM) and this led to an understanding of the structure of the assembled film. The assembled film structure was further characterized using electron spectroscopy for chemical analysis (ESCA) and secondary ion mass spectrometry (SIMS).

Scanning probe microscopy and scanning tunneling spectroscopy of porous silicon

1992 ◽  
Vol 61 (21) ◽  
pp. 2595-2597 ◽  
Author(s):  
G. B. Amisola ◽  
R. Behrensmeier ◽  
J. M. Galligan ◽  
F. A. Otter ◽  
F. Namavar ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Scanning Probe Microscopy ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Probe Microscopy

Industrial Applications of Scanning Probe Microscopy

1998 ◽  
Vol 4 (S2) ◽  
pp. 522-523
Author(s):  
S. Magonov
Keyword(s):  
Scanning Probe Microscopy ◽  
High Vacuum ◽  
Sample Surface ◽  
Industrial Applications ◽  
Ultra High Vacuum ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Probe Microscopy ◽  
Force Microscopy

The evolution of scanning tunneling microscopy (STM) into atomic force microscopy (AFM) have led to a family of scanning probe techniques which are widely applied in fundamental research and in industry. Visualization of the atomic- and molecular-scale structures and the possibility of modifying these structures using a sharp probe were demonstrated with the techniques on many materials. These unique capabilities initiated the further development of AFM and related methods generalized as scanning probe microscopy (SPM). The first STM experiments were performed in the clean conditions of ultra-high vacuum and on well-defined conducting or semi-conducting surfaces. These conditions restrict SPM applications to the real world that requires ambient-condition operation on the samples, many of which are insulators. AFM, which is based on the detection of forces between a tiny cantilever carrying a sharp tip and a sample surface, was introduced to satisfy these requirements. High lateral resolution and unique vertical resolution (angstrom scale) are essential AFM features.

Scanning-probe microscopy of polymers

1993 ◽  
Vol 51 ◽  
pp. 874-875
Author(s):  
Darrell H. Reneker ◽  
Rajkumari Patil ◽  
Seog J. Kim ◽  
Vladimir Tsukruk
Keyword(s):  
Scanning Probe Microscopy ◽  
Domain Boundary ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Lamellar Crystal ◽  
Probe Microscopy ◽  
Atomic Force ◽  
Resolution Observation ◽  
Lamellar Crystals

Scanning probe microscopy techniques, particularly atomic force microscopy (AFM) and scanning tunneling microscopy (STM) are finding a rapidly growing number of applications to both synthetic and biological polymers. Segments of individual polymer molecules can often be observed with atom scale resolution. Observation of polymeric objects as large as 100 microns with nanometer resolution is possible with contemporary AFM, although features caused by the convolution of the shape of the sample and the shape of the tip must be recognized and properly interpreted. The vertical resolution of the atomic force microscope readily provides precise data about the heights of molecules, crystals, and other objects.Lamellar crystals of polyethylene are well characterized objects with many features which can be observed with scanning probe microscopes. Figure 1 shows the fold surface near a fold domain boundary of a lamellar crystal of polyethylene, as observed with an AFM. The folded chain crystal is about 15 nm thick.

scholarly journals Pure hydrogen low-temperature plasma exposure of HOPG and graphene: Graphane formation?

2012 ◽  
Vol 3 ◽  
pp. 852-859 ◽  
Author(s):  
Baran Eren ◽  
Dorothée Hug ◽  
Laurent Marot ◽  
Rémy Pawlak ◽  
Marcin Kisiel ◽  
...  
Keyword(s):  
Low Temperature ◽  
Scanning Probe Microscopy ◽  
Atomic Scale ◽  
Scanning Probe ◽  
Scanning Tunneling ◽  
Multilayer Graphene ◽  
Pure Hydrogen ◽  
Low Temperature Plasma ◽  
Temperature Plasma ◽  
Probe Microscopy

Single- and multilayer graphene and highly ordered pyrolytic graphite (HOPG) were exposed to a pure hydrogen low-temperature plasma (LTP). Characterizations include various experimental techniques such as photoelectron spectroscopy, Raman spectroscopy and scanning probe microscopy. Our photoemission measurement shows that hydrogen LTP exposed HOPG has a diamond-like valence-band structure, which suggests double-sided hydrogenation. With the scanning tunneling microscopy technique, various atomic-scale charge-density patterns were observed, which may be associated with different C–H conformers. Hydrogen-LTP-exposed graphene on SiO2 has a Raman spectrum in which the D peak to G peak ratio is over 4, associated with hydrogenation on both sides. A very low defect density was observed in the scanning probe microscopy measurements, which enables a reverse transformation to graphene. Hydrogen-LTP-exposed HOPG possesses a high thermal stability, and therefore, this transformation requires annealing at over 1000 °C.

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