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The Scientific Basis of Medicine
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Chris O'Callaghan, Rachel Allen
Proteins are long chains of amino acids held together by peptide bonds. Each amino acid is composed of an amino group, a carboxyl group and the particular side chain that defines their chemical nature. Individual proteins are constructed from a library of 20 amino acids, which may be subgrouped according to the acidic, basic, uncharged polar or non-polar character of their side chains (Figure 2.2). Like all large molecules, proteins adopt a conformation that confers the most stability. Protein modifications can result from the addition of other substances, such as metal ions (e.g. iron in haemoglobin), lipids (lipoproteins) or carbohydrates (glycoproteins).
Macronutrients
Published in Chuong Pham-Huy, Bruno Pham Huy, Food and Lifestyle in Health and Disease, 2022
Chuong Pham-Huy, Bruno Pham Huy
Amino acids (AA) are organic nitrogenous compounds containing both an acidic carboxyl (-COOH) and a basic amino (-NH2) group attached to a central α-carbon. They are called α-amino acids and are classified as proteins (37–39). The first carbon is part of the carboxyl group. The second carbon, to which is attached the amino group, is called the α-carbon. The α-carbon of most amino acids is joined by covalent bonds to four different groups. Thus, the α-carbon in all the amino acids is asymmetric, except in glycine where the α-carbon is symmetric. In some amino acids, the amine group is attached to the β or γ-carbon, and these are therefore referred to as beta or gamma amino acids (38–39).
Components of Nutrition
Published in Christopher Cumo, Ancestral Diets and Nutrition, 2020
Ignoring the carboxyl group mentioned earlier and within a rectangle in Figure 2.7, each carbon forms two bonds with hydrogen atoms and the other two with adjacent carbons. Aside from the carboxyl group, no carbon has a double bond with another atom.
Advances in phosphoproteomics and its application to COPD
Published in Expert Review of Proteomics, 2022
Xiaoyin Zeng, Yanting Lan, Jing Xiao, Longbo Hu, Long Tan, Mengdi Liang, Xufei Wang, Shaohua Lu, Tao Peng, Fei Long
In strong cation exchange (SCX) chromatography, the stationary phase particles of SCX are negatively charged functional groups, and acidic conditions promote interaction between the positively charged tryptic peptides and the SCX particles. Beausoleil et al. [60] found that at pH = 2.7, the carboxyl group would be protonated. The phosphopeptide will retain the negative charge on the phosphate group, causing the tryptic peptide to change from a + 2 charge to a + 1 charge. Hence, the phosphopeptide interacts less with the stationary phase. It is therefore eluted from the column earlier, separating the phosphorylated peptide from the nonphosphorylated peptide (Figure 2a). However, the protein digestion process is prone to missing cleavage sites, affecting the charge number of peptides after digestion and resulting in some phosphopeptides not being eluted first but simultaneously being eluted down with nonphosphorylated peptides. Therefore, to increase the separation effect of SCX, some researchers are now using the SCX method in combination with IMAC, MOAC, and other chemical derivatization methods to improve the separation and identification of phosphopeptides. For example, Gruhler’s group [61] and Trinidad’s group [62] reported that the number of phosphopeptides identified was greatly improved by the total proteins being enzymatically cleaved into peptides by SCX during the first fractionating followed by further enrichment of phosphopeptides using IMAC.
Nutraceuticals-based therapeutic approach: recent advances to combat pathogenesis of Alzheimer’s disease
Published in Expert Review of Neurotherapeutics, 2021
Marjan Talebi, Eleni Kakouri, Mohsen Talebi, Petros A. Tarantilis, Tahereh Farkhondeh, Selen İlgün, Ali Mohammad Pourbagher-Shahri, Saeed Samarghandian
Biologically important molecules that have long attracted scientists’ interest are the carotenoids derived from the plant of Crocus sativus L, and specifically from its red stigmas, namely crocins (CRCs) and crocetin [150]. There are five different types of CRCs identified at the stigmas of the plant which differ at the sugar moiety attached at the terminals of the carbohydrate skeleton [151]. Because of their glycosylated ends, CRCs are water-soluble carotenoids. On the other hand, crocetin a dicarboxylic acid, basically the aglycon part of CRCs, is found in minor quantity with respect to CRCs. Each terminal part of the carbohydrate skeleton is occupied by a carboxyl group (-COOH). Both molecules are capable of delaying the progression of neurodegenerative disorders, such as Alzheimer’s disease [152]; as we describe below.
Liver-targeted delivery of asiatic acid nanostructured lipid carrier for the treatment of liver fibrosis
Published in Drug Delivery, 2021
Ya-Wen Zhang, Ling-Lan Tu, Yi Zhang, Jie-Chao Pan, Gao-Li Zheng, Li-Na Yin
Figure 1(B) shows the spectra of the structures of intermediate and final products verified by 1H NMR. The signals at δ 4.54–4.64 ppm in Figure 1(B) (a) were attributed to the hydrogen attached to the acetoxy group of UA. No signal peaks were observed between δ 3.87 and 4.45 (the two hydroxyl groups of UA) (Zhang et al., 2019), demonstrating the acetylation of the carboxyl group on UA. The carboxyl active hydrogen of acetyl ursodeoxycholic acid (Figure 1(B) (a)) was δ 11.96 ppm; however, the peak disappeared (Figure 1(B) (b)), indicating complete esterification of the carboxyl group on UA. Additionally, two strong hydrogen signal peaks occurred at δ 3.51 and 1.23 ppm (hydrogen of polyethylene glycol and stearic acid, respectively (Figure 1(B) (b)); however, no other active hydrogen signals were reported, which demonstrate successful esterification of the target product UA-PEG-SA.