Area Of Amide Research Articles

Monitoring the curing efficiency of a plant-based green engineered additive on caprine skin: a spectroscopic and chemometric novel approach

Environmental sustainability in industrial processing is one of the most fundamental requirements for sustainable development. The leather industry is known for its vast environmental pollution. But, green engineering may occur a paradigm shift in this sector. Plant-based goatskins curing is a cutting-edge green technology that holds the concept of pollution reduction through prevention on the upper stream of leather processing. The successful and rapid monitoring of the efficiency of this technology is the foremost demand for mass-level applications. In this study, ATR-FTIR spectroscopy was employed to monitor this technology's efficiency using a plant Polygonum hydropiper. Chemometrics was also applied to extract information from spectral data leading to an understanding of the inherent effect of studying preservatives on goatskins collagen chemistry. 10% plant-paste +5% NaCl, 10% plant-paste +10% NaCl, and 15% plant-paste +5% NaCl on goatskin were assessed by ATR-FTIR on 0th, 10th, and 30th days of preservation. The Spectral peak fitting (R2 = 0.99) area of amide I and II of collagen peptide bands revealed 2.73 to 1.33 times more structural suitability of studied goatskins than the control. Principal component analysis and Hierarchical cluster analysis showed that, after 30 days of curing, 15% paste +5% salt-rubbed goatskin collagen matrix significantly (around 50%) interacted with P. hydropiper. The interaction was superficial, as it happened before the opening up of collagen fibers. In conclusion, ATR-FTIR spectroscopy with Chemometrics can be an effective tool in evaluating the efficiency of goatskin curing and understanding the entire effect on collagen chemistry quickly.

Changes in molecular structure of protein and carbohydrate in soybean products with different processing methods and their effects on nutrient degradation characteristics of the products

In this study, four types of soybean products with different processing methods (soybean meal 1 and soybean meal 2, extruded soybean meal, fermented soybean meal and extruded soybean) were used to examine the effect of fermentation and extrusion on molecular structures of protein and carbohydrate. Extrusion and fermentation significantly decreased (P < 0.05) the values of related protein spectral intensities (height and area of amide and secondary structure) and the biggest reduction was found in extruded soybean compared to soybean meal 1 and soybean meal 2. Compared with extruded soybean meal, the area ratio of amide I to amide II and the height ratio of α-helix to β sheet in extruded soybean were significantly reduced (P < 0.05), and there was no difference in these spectral values between extruded and fermented soybean. Extrusion and fermentation significantly decreased (P < 0.05) the values of carbohydrate spectral intensities, including structural carbohydrate (STCHO) and cellulosic compounds (CELC) and total carbohydrate (CHO), compared to soybean meal 2. The ratio of α-helix to β-sheet was positively related to the DM of soybean degradability in the rumen (P < 0.05, r = 0.590), so was A-CELC to A-STCHO (P < 0.05, r = 0.747). A positive relationship was found between CP degradability in the rumen and the area ratios of amide I and amide II, CELC to CHO, and STCHO to CHO. Spectral intensity of CHO area was negatively associated with neutral detergent fibre (NDF) and acid detergent fibre (ADF) degradability in the rumen. The study indicated that extrusion and fermentation could alter the molecular structure of protein and carbohydrate and the degradation characteristics of soybean products in the rumen.

Breaking Amides using Nickel Catalysis.

Amides have been widely studied for decades, but their synthetic utility has remained limited in reactions that proceed with rupture of the amide C-N bond. Using Ni catalysis, we have found that amides can now be strategically employed in several important transformations: esterification, transamidation, Suzuki-Miyaura couplings, and Negishi couplings. These methodologies provide exciting new tools to build C-heteroatom and C-C bonds using an unconventional reactant (i.e., the amide), which is ideally suited for use in multi-step synthesis. It is expected that the area of amide C-N bond activation using nonprecious metals will continue to flourish and, in turn, will promote the growing use of amides as synthons in organic synthesis.

Lipid Composition Regulates the Orientation of Transmembrane Helices in HorA, an ABC Multidrug Transporter

ATP-binding cassette (ABC) transporters constitute a large class of molecular pumps whose central role in chemotherapy resistance has highlighted their clinical relevance. We investigated whether the lipid composition of the membrane affects the function and structure of HorA, a bacterial ABC multidrug transporter. When the transporter was reconstituted in a bilayer where phosphatidylethanolamine (PE), the main lipid of the bacterial membrane, was replaced with phosphatidylcholine (PC), ATP hydrolysis and substrate transport became uncoupled. Although ATPase activity was maintained, HorA lost its ability to extrude the prototypical substrate Hoechst33342. Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) revealed that, although the secondary structure of the protein was unaffected, the orientation of the transmembrane helices (TM) was modified by the change in lipid composition. The orientation of the backbone carbonyls indicated that the helices opened wider in PE versus PC-containing liposomes, with 10 degrees difference. This was supported by hydrogen/deuterium exchange studies showing increased protection of the backbone from the solvent in PC-containing liposomes. Electron Paramagnetic Resonance was used to further probe the structural change. In the PC-containing liposomes we observed increased mobility of the spin label in TM4, along with increased exposure to molecular oxygen, used as a hydrophobic quencher. This indicates that the lipid change induced modification of the orientation of TM4, exposing Cys-180 to the lipid phase. The lipid composition of the bilayer thus modulates the structure of HorA, and in turn its ability to extrude its substrates.

Assessing secondary structure of a dyed wool fibre by means of FTIR and FTR spectroscopies

The paper describes changes in the structure of a wool fibre dyed with model azo dyes. These were direct dyes, non-genotoxic derivatives of carcinogenic benzidine, synthesized specially for the purpose of the experiment. The non-mutagenic benzidine derivatives were: 2,2′-dimethyl-5,5′-dipropoxybenzidine and 5,5′-dipropoxybenzidine. Using FTIR, changes in secondary structure of fibres were assessed in three measuring ranges: 3600–3000, 1700–1400 and 1000–1300 cm −1. The dyes were found to distinctively affect wave-number shifts of amide A, amide I bands and in the fingerprint area around 1050 cm −1. It seems that these three areas are related to the sites in which dyes bind with wool fibre keratin. In FTR spectra, the focus was on assessing the changes of peptide bond configuration in the area of amide I, disulfide area of cystine and the area of the interaction between dyes and wool fibre keratin, i.e. 1250–1600 cm −1. For analysis, three kinds of materials were selected: (1) raw wool fibres, (2) fibres subjected to deuteration and treated with formic acid, (3) wool fabric. Each of them was dyed with the model azo dyes. The results obtained by both spectroscopies allow for identifying the functional groups responsible for the binding of dyes with keratin fibre.

PH-dependent secondary conformation of the peptide hormone leptin in different buffer solutions.

The secondary structure of leptin in each different pH buffer solution (pH 5.35, 6.75, 7.58 and 8.45) was first determined by attenuated total reflection (ATR)/Fourier transform infrared (FT-IR) spectrometer with second-derivative, Fourier self-deconvolution and band curve-fitting methods to quantitatively estimate the secondary structure of leptin. The results indicate that pH induced more stretching vibration of CH2 and bending vibration of C-H and/or symmetric stretching of carboxylate of leptin structure in higher pH buffer solution than in lower pH buffer solution. Moreover, the band area of amide I for leptin in the higher pH buffer solution markedly enlarged, suggesting the amide I contour of leptin was very sensitive to pH to alter the secondary conformation of leptin structure. The structural component and composition of amide I band for leptin in both pH 6.75 and pH 7.58 buffer solutions were similar and had 50-52% helical structure including alpha-helix at 1654 cm-1 and 3(10)-helical structure at 1659-1667 cm-1 and 1640 cm-1. Although the secondary structure of leptin in pH 5.35 and 8.45 buffer solutions were also similar, a different structural information was obtained.