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Formation of toxic oligomeric and fibrillar structures by the amyloid beta-protein (Abeta) is linked to Alzheimer's disease (AD). To facilitate the targeting and design of assembly inhibitors, intrinsic fluorescence was used to probe assembly-dependent changes in Abeta conformation. To do so, Tyr was substituted in Abeta40 or Abeta42 at position 1, 10 (wild type), 20, 30, 40, or 42. Fluorescence then was monitored periodically during peptide monomer folding and assembly. Electron microscopy revealed that all peptides assembled readily into amyloid fibrils. Conformational differences between Abeta40 and Abeta42 were observed in the central hydrophobic cluster (CHC) region, Leu17-Ala21. Tyr20 was partially quenched in unassembled Abeta40 but displayed a significant and rapid increase in intensity coincident with the maturation of an oligomeric, alpha-helix-containing intermediate into amyloid fibrils. This process was not observed during Abeta42 assembly, during which small decreases in fluorescence intensity were observed in the CHC. These data suggest that the structure of the CHC in Abeta42 is relatively constant within unassembled peptide and during the self-association process. Solvent accessibility of the Tyr ring was studied using a mixed solvent (dimethyl sulfoxide/water) system. [Tyr40]Abeta40, [Tyr30]Abeta42, and [Tyr42]Abeta42 all were relatively shielded from solvent. Analysis of the assembly dependence of the site-specific intrinsic fluorescence data suggests that the CHC is particularly important in controlling Abeta40 assembly, whereas the C-terminus plays the more significant role in Abeta42 assembly.

Formation of toxic oligomeric and fibrillar structures by the amyloid beta-protein (Abeta) is linked to Alzheimer's disease (AD). To facilitate the targeting and design of assembly inhibitors, intrinsic fluorescence was used to probe assembly-dependent changes in Abeta conformation. To do so, Tyr was substituted in Abeta40 or Abeta42 at position 1, 10 (wild type), 20, 30, 40, or 42. Fluorescence then was monitored periodically during peptide monomer folding and assembly. Electron microscopy revealed that all peptides assembled readily into amyloid fibrils. Conformational differences between Abeta40 and Abeta42 were observed in the central hydrophobic cluster (CHC) region, Leu17-Ala21. Tyr20 was partially quenched in unassembled Abeta40 but displayed a significant and rapid increase in intensity coincident with the maturation of an oligomeric, alpha-helix-containing intermediate into amyloid fibrils. This process was not observed during Abeta42 assembly, during which small decreases in fluorescence intensity were observed in the CHC. These data suggest that the structure of the CHC in Abeta42 is relatively constant within unassembled peptide and during the self-association process. Solvent accessibility of the Tyr ring was studied using a mixed solvent (dimethyl sulfoxide/water) system. [Tyr40]Abeta40, [Tyr30]Abeta42, and [Tyr42]Abeta42 all were relatively shielded from solvent. Analysis of the assembly dependence of the site-specific intrinsic fluorescence data suggests that the CHC is particularly important in controlling Abeta40 assembly, whereas the C-terminus plays the more significant role in Abeta42 assembly.

A low-temperature Fourier transform infrared (FTIR) difference spectroscopy was used to examine the structural changes during the primary photoreaction in blue-absorbing proteorhodopsin (BPR), a light-driven retinylidene proton pump. The significant differences observed between the two types of proteorhodopsin (BPR and green-absorbing proteorhodopsin (GPR)) during the initial photoreaction despite their similar chromophore structures have shown a different arrangement of water in the active site as well as substitution of a hydrophilic for hydrophobic residue at residue 105.

A combination of visible and infrared spectroscopy is used to explore the difference in the protonation state of a glutamic acid residue located at position 142 (Glu142) on the extracellular side of helix D. Glu142 in the green- and blue-absorbing proteorhodopsin (GPR and BPR) exhibits three distinctive photocycles depending upon the pH of its native marine environment and changes in pH might modulate its function in the cell.

Faster subpicosecond protein responses are tested by examining the earliest protein structural changes occurring in proteorhodopsin (PR). One or more peptide backbone groups in PR have responded with a time constant of 500-700 fs and the protein changes are involved in storage of the absorbed photon energy.

Proteobacteria is found in ocean waters and is important to the global solar energy input in the biosphere. Structural changes are examined during the primary photoreaction of this proteobacteria and the results suggest that significant differences exist in the conformational changes, which occur in the photoactive sites of proteorhodopsin and bacteriorhodopsin during the primary phtoreaction.

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer’s compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified.ᅟ [ABSTRACT FROM AUTHOR]