Biochemical and morpho-mechanical properties, and structural organization of rat tail tendon collagen in diet-induced obesity model

We have investigated the impact of obesity on the structural organization, morpho-mechanical properties of collagen fibers from rat tail tendon fascicles (RTTFs). Polarized Raman microspectroscopy showed that the collagen bands 855, 875, 938, and 960 cm-1 as well as those 1631 and 1660 cm-1 were affected by diet. Mechanical properties exhibited an increase in the yield strength from control (CTRL) to high fat (HF) diet (9.60 ± 1.71 and 13.09 ± 1.81 MPa) (p < 0.01) and ultimate tensile strength (13.12 ± 2.37 and 18.32 ± 2.83 MPa) (p < 0.05) with no significant change in the Young's Modulus. During mechanical, the band at 875 cm-1 exhibited the most relevant frequency shift (2 cm-1). The intensity of those at 855, 875, and 938 cm-1 in HF collagen displayed a comparable response to mechanical stress as compared to CTRL collagen with no significant diet-related changes in the Full Width at Half Maximum. Second harmonic generation technique revealed i) similar fiber straightness (0.963 ± 0.004 and 0.965 ± 0.003) and ii) significant changes in fibers diameter (1.48 ± 0.07 and 1.52 ± 0.08 μm) (p < 0.05) and length (22.06 ± 2.38 and 29.00 ± 3.76 μm) (p < 0.001) between CTRL and HF diet, respectively. The quantification of advanced glycation end products (AGEs) revealed an increase in both carboxymethyl-lysine and total fluorescence AGEs from CTRL to HF RTTFs.

Proteomics and metabolomics composition of the ink of a letter in a fragment of a Dead Sea Scroll from Cave 11 (P1032-Fr0)

It is well established that the ink pigment used for writing the Dead Sea Scrolls (DSS) is mainly composed of carbon soot. The ink's binder however has yet to be securely identified. By applying EVA (ethylene vinyl acetate containing strong anion and cation exchangers admixed with C₈ and C₁₈) diskettes on one fragment and analyzing the captured material, the following study was able to determine the composition of the binder. Proteins admixed of plant proteins (ribulose biphosphate carboxylase, rhamnogalacturonate lyase, α-galactosidase A, calmodulin, among those identified) as well as of a few glycoproteins with different combinations of pentosyl and hexosyl units with plant acids (stearic, palmitic, oleic, linoleic and linolenic acids) and terpenes (triacontanol, catechin, lupeol) are mixed attributes of acacia trees which suggests the use of gum Arabic as the ink's binder. SIGNIFICANCE: Whereas a huge body of reports has explored any possible aspect of the Dead Sea Scrolls, including the dating and the animal origin of the parchment, one aspect had not been investigated so far, namely which kind of ligand had been adopted to ensure a firm binding of the ink (in reality carbon soot) to the supporting parchment. In the present investigation it has been demonstrated that this "glue" is a mixture of plant proteins, as well as a few glycoproteins, together with plant acids and terpenes. These proteins and metabolites belong to two species of trees, Vachellia nilotica and Acacia Albida, widespread in this Middle East region. The EVA methodology here adopted has shown that it is possible to explore any item pertaining to the world Cultural Heritage in the absence of damage or contamination thus permititng to analyze any possible precious document stored in museum, public libraries and private collections.

The Temple Scroll: Reconstructing an ancient manufacturing practice

The miraculously preserved 2000-year-old Dead Sea Scrolls, ancient texts of invaluable historical significance, were discovered in the mid-20th century in the caves of the Judean desert. The texts were mainly written on parchment and exhibit vast diversity in their states of preservation. One particular scroll, the 8-m-long Temple Scroll is especially notable because of its exceptional thinness and bright ivory color. The parchment has a layered structure, consisting of a collagenous base material and an atypical inorganic overlayer. We analyzed the chemistry of the inorganic layer using x-ray and Raman spectroscopies and discovered a variety of evaporitic sulfate salts. This points toward a unique ancient production technology in which the parchment was modified through the addition of the inorganic layer as a writing surface. Furthermore, understanding the properties of these minerals is particularly critical for the development of suitable conservation methods for the preservation of these invaluable historical documents.

Age-related changes in molecular organization of type I collagen in tendon as probed by polarized SHG and Raman microspectroscopy

Type I Collagen is one of the most abundant proteins of the extracellular matrix of the most organs. During chronological aging or in diseases, type I collagen undergoes biochemical and structural changes which can impact biomechanical and physiological properties of organs. In this study, we have investigated the age-related changes in the molecular organization of type I collagen in rat tails tendon using polarized Raman spectroscopy. Our results show that Amide I, amide III as well as the bands related to proline and hydroxyproline are highly sensitive to polarization and age-related. On the other hand, 1453 and 1270 cm⁻¹ do not show any preferential orientation. Depolarization and anisotropic ratios were used to provide information about the changes in orientation of collagen fibers with aging. The anisotropy degree of Raman bands increase from adult to old collagen, indicating a higher collagen fibers alignment to the fascicle backbone axis in old tendons, and consequently a higher straightness of collagen fibers. These data were correlated to those obtained using polarized second harmonic generation technique. Polarized Raman mapping showed a more homogeneous spatial distribution of collagen fibers alignment to the fascicle axis in old tendon. This confirms a higher straightness of collagen fiber with aging.

Novel Raman Spectroscopic Biomarkers Indicate That Postyield Damage Denatures Bone's Collagen

Raman spectroscopy has become a powerful tool in the assessment of bone quality. However, the use of Raman spectroscopy to assess collagen quality in bone is less established than mineral quality. Because postyield mechanical properties of bone are mostly determined by collagen rather than the mineral phase, it is essential to identify new spectroscopic biomarkers that help infer the status of collagen quality. Amide I and amide III bands are uniquely useful for collagen conformational analysis. Thus, the first aim of this work was to identify the regions of amide bands that are sensitive to thermally induced denaturation. Collagen sheets and bone were thermally denatured to identify spectral measures that change significantly following denaturation. The second aim was to assess whether mechanical damage denatures the collagen phase of bone, as reflected by the molecular spectroscopic biomarkers identified in the first aim. The third aim was to assess the correlation between these new spectroscopic biomarkers and postyield mechanical properties of cortical bone. Our results revealed five peaks whose intensities were sensitive to thermal and mechanical denaturation: ∼1245, ∼1270, and ∼1320 cm(-1) in the amide III band, and ∼1640 and ∼1670 cm(-1) in the amide I band. Four peak intensity ratios derived from these peaks were found to be sensitive to denaturation: 1670/1640, 1320/1454, 1245/1270, and 1245/1454. Among these four spectral biomarkers, only 1670/1640 displayed significant correlation with all postyield mechanical properties. The overall results showed that these peak intensity ratios can be used as novel spectroscopic biomarkers to assess collagen quality and integrity. The changes in these ratios with denaturation may reflect alterations in the collagen secondary structure, specifically a transition from ordered to less-ordered structure. The overall results clearly demonstrate that this new spectral information, specifically the ratio of 1670/1640, can be used to understand the involvement of collagen quality in the fragility of bone. © 2015 American Society for Bone and Mineral Research.

Differentiation of aged fibers by Raman spectroscopy and multivariate data analysis

Raman spectroscopy followed by multivariate data analysis was used to analyze cotton fibers dyed using similar formulations and submitted to different aging conditions. Spectra were collected on a commercial instrument using a near-infrared laser with a 780nm light source. Discriminant analysis allowed to correctly classify the aged fibers 100% of the time. The prediction ability of the calculated model was estimated to be 100% by the "leave-one-out" cross-validation for 3 out of the 4 series under investigation. Finally, reliability of the developed approach for the discrimination of aged vs new fibers was confirmed by the analysis of commercial polyamide and polyester textiles submitted to the same aging process.