mohamed elmalatawy

Abstract The conformational changes of the bovine lens protein “α-crystallin” have been investigated in the presence of the photosensitizer Rose Bengal (RB), in the dark as well as after visible light irradiation. Absorption and fluorescence emission spectra of RB [5 × 10−6 m] and Fourier transform-IR spectra of α-crystallin [5 mg mL−1] were significantly altered upon RB α-crystallin complex formation. RB was found to bind to α-crystallin in a molecular pocket characterized by a low polarity, with Trp most likely involved in this interaction. The binding constant (Kb) has been estimated to be of the order of 2.5 (mg/mL)−1. The intrinsic fluorescence of α-crystallin was quenched through both dynamic and static mechanisms. Light-induced photosensitized effects showed structural modifications in α-crystallin, including tertiary and secondary structure (an increase in unordered structure) alterations. Notwithstanding those photoinduced structural variations detected in α-crystallin when complexed with RB, the protein still retains its ability to play the role of chaperone for β-crystallin.

Bones are mostly composed of analogous volume fractions of collagen as organic material and apatite as minerals. After burial, bones undergo several complicated depositional variations in the calcified tissues (diagenesis). Since bones are hard tissues, they can confer many crucial and vital data. Fourier transform infrared (FTIR) microspectroscopy is a powerful molecular spectroscopic tool that can trace the molecular changes with high spatial resolution. The current research is a case study that is aimed at probing the diagenetic changes across different depth sections of two bone shafts by transmission FTIR imaging and chemometric analysis. Amide I, carbonyl, carbonate, and phosphate bands as well as the indices of amide I/phosphate and V3-carbonate/phosphate ratios were used to construct chemical images of the bone shafts belonging to two ancient Egyptian dynasties, namely, Roman Greek (RG) period and late period (LP). Chemical images showed different chemical distribution in the external part of the two bone shafts. Principal component analysis efficiently discriminated between the investigated bones and between various depth regions from the same bone section.

ABSTRACT Bones are mainly composite materials of equivalent volume fractions of mineral (apatite) and organic (collagen) parts. Their infrared spectroscopic characteristics mirror their composition. Bone diagenesis is the post-depositional changes of calcified tissues by chemical degradation. It is a complicated process and affected by numerous external and individual factors. Diagenetic trajectories have been employed using Fourier transform infrared (FTIR) spectroscopy to monitor the preservation status of bioapatite. We studied the diagenesis in ancient Egyptian bones of four dynasties collected from two different locations – Sakkara and Aswan using attenuated total reflectance (ATR) FTIR microspectroscopy. Despite the latter is a promising technique since it is a minimally destructive tool, the samples’ physical properties may affect the data accuracy. The studied bone pieces were from two sites, the shaft and the femur head. Transmission electron microscopy (TEM) was used to investigate the bone crystals size and shape. ATR-FTIR spectrographs showed different molecular fingerprints between Sakkara and Aswan soil samples. The technique was able to monitor different molecular structures across the shaft bones indicating different diagenetic grades. TEM micrographs showed low abundant crystals of needle shaped for Late period shaft bones, while those from Roman Greek period were characterized with abundant irregular thin platelet crystals.

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