Low-frequency vibrational spectroscopy of proteins with different secondary structures.

Fourier transform infrared (FTIR) and Raman spectra of proteins with significantly different structures are measured in a spectral interval of 50 to 500 ?? cm ? 1 and noticeable spectral differences are revealed. Intensities of several spectral bands correlate with contents of secondary structure elements. FTIR spectra of superhelical proteins exhibit developed spectral features that are absent in the spectra of globular proteins. Significant differences of the Raman spectra of proteins that are not directly related to the difference of the secondary structures can be due to differences of tertiary and/or quaternary structure of protein molecules.

Fourier Transform Infrared (FT-IR) Microspectroscopy of 20th Century Russian Oil Paintings: Problem of Dating.

Analysis of the IR spectra of samples from 230 Russian oil paintings of the 20th century is used to propose a procedure for the threshold estimation of the age of paintings based on measured parameters (intensity ratios of spectral bands). The bands of compounds that are formed upon interaction of pigment (zinc white) with oil are used for dating.

Raman microspectroscopy of nanodiamond-induced structural changes in albumin.

Nanodiamonds (NDs) are promising agents for theranostic applications due to reported low toxicity and high biocompatibility, which is still being extensively tested on cellular, tissue, and organism levels. It is presumed that for experimental and future clinical applications, NDs will be administered into the organism via the blood circulation system. In this regard, the interaction of NDs with blood components needs to be thoroughly studied. We studied the interaction of carboxylated NDs (cNDs) with albumin, one of the major proteins of blood plasma. After 2-h long in vitro incubation in an aqueous solution of the protein, 100-nm cNDs were dried and the dry samples were studied with the aid of Raman microspectroscopy. The spectroscopic data indicate significant conformational changes that can be due to cND­protein interaction. A possible decrease in the functional activity of albumin related to the conformational changes must be taken into account in the in vivo applications.

Effect of thermal denaturation, inhibition, and cleavage of disulfide bonds on the low-frequency Raman and FTIR spectra of chymotrypsin and albumin.

The analysis of the structure-function relationship is extremely important in the study of proteins. The importance of function-related motions of large parts or subglobules of protein molecules stimulates the spectroscopic study in the low-frequency (terahertz) domain. However, only tentative assignments are available and the spectroscopic data are insufficiently discussed in terms of structural changes. This work is aimed at the analysis of regularities of changes in the low-frequency (100 to 600 cm(-1)) FTIR and Raman spectra of proteins related to their structural modifications. We study the spectra of two proteins with substantially different structures (albumin and chymotrypsin) and the spectra of samples in which the structures of protein molecules are modified using inhibition, thermal denaturation, and cleavage of disulfide bonds. The results indicate that the low-frequency spectral interval can be used to characterize protein conformations. Correlated variations in the intensities of several low-frequency bands are revealed in the spectra of the modified proteins. The strongest spectral changes are caused by thermal denaturation of proteins, and the effect of cleavage of disulfide bonds is generally weaker. It is demonstrated that the inhibitor binding in the active site causes spectral changes that can be compared to the changes induced by thermal denaturation.

Raman microspectroscopy of old paper samples with foxing.

Diagnostic methods and historical document and artwork (in particular, paper items) analysis using modern physical methods is a topical practical problem. Paper materials exhibit nonuniform degradation with the formation of foxing stains. Correct physicochemical identification of the structure of foxed fragments depends on the efficiency of the experimental technique and offers guidelines for restoration. Raman spectroscopy makes it possible to characterize old paper samples; however, to our knowledge, a comprehensive Raman analysis of foxing has not been done. In this study, we demonstrate that Raman microspectroscopy allows the identification of spectral changes related to paper aging and foxing formation. The degree of degradation of the rag papers studied here is noticeably less than the degree of degradation of the wood-cellulose papers. The spectral differences among 19(th)-, 20(th)-, and 21(st)-century papers are revealed. The presence of lignin and gypsum filler in the 20th-century paper is demonstrated. Raman data indicate that the foxed fragments exhibit a stronger degradation of the paper. The spectral differences between the foxed and unfoxed fragments are discussed. The results can be used in the restoration of paper documents and artworks, in particular for identification of foxed fragments.