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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).
Fundamentals of Modern Peptide Synthesis
Published in Mesut Karahan, Synthetic Peptide Vaccine Models, 2021
Amino acids in peptides and proteins are linked together with a peptide bond. The peptide bond is a chemical bond formed between two molecules of amino acids when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water. This is a dehydration synthesis reaction (also known as a condensation reaction), and usually occurs between amino acids. Dipeptide is the structure formed by the combination of two amino acids with amide bond. Likewise, as amino acids are added, we may have tripeptides, tetrapeptides, and other polypeptides. Gradually, when the structure moves towards quaternary structures, it is called protein (Raven et al. 2014; Reece et al. 2011).
Vasoconstrictors: Chemistry, Mode of Action, and Dosage
Published in Marwali Harahap, Adel R. Abadir, Anesthesia and Analgesia in Dermatologic Surgery, 2019
Peptides are a group of amino acids connected by an amide or peptide bond. They are similar to, but smaller than, proteins. They are responsible for a wide variety of functions, many of which are not yet understood. Peptides are important in cell-to-cell communication. Several peptides possess vasoconstriction properties. These include vasopressin, angiotensin II, endothelins, urotensin, and neuropeptide Y.
Impact of Aluminium phthalocyanine nanoconjugate on melanoma stem cells
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2023
Bridgette Mkhobongo, Rahul Chandran, Heidi Abrahamse
The qualitative molecular features were studied by means of Fourier transform infra-red spectroscopy (FTIR). Peptide bonds as well as ligand and absorption bond forms could be identified. Figure 3 depicts the outcomes. The conjugate was suspended in distilled deionised water (ddH20) and O-H stretching could be recognised at 3286.9 cm−1. The O-H bending was observed at 1363.1 – 1540 cm−1 due to carboxylic acid. C=C stretching was observed at 1540 cm−1. The polyether structure in PEG resulted in the C-O stretching, observed at 1038.8 cm−1. Due to the PS's structural elements, including its benzene rings and the PEG that was already present on the NP, the AlPcS4Cl-AuNP-PEG-COOH conjugate demonstrated C=C stretching at 1540 cm−1. The alkane methyl group’s translation into the C-H bending at 1471 cm−1 comes from the PS structure. The O-H bending from carboxylic acid was seen at 1430 cm−1, S=O stretching at 130 8.8 cm−1. The PS with sulphate functionalization was seen at 107.2 cm−1.
Emerging peptide therapeutics for the treatment of ovarian cancer
Published in Expert Opinion on Emerging Drugs, 2023
Ana C. Veneziani, Eduardo Gonzalez-Ochoa, Amit M. Oza
Peptides are composed of short sequences of amino acids and are held together by peptide bonds. They are structural segments of proteins and are subdivided into oligopeptides and polypeptides [42]. Therapeutic peptides and proteins bind to cell receptors with high affinity and trigger intracellular effects. They are vital for cellular activity, such as cell growth, energy metabolism, material transport, signal transmission, and immune regulation [43–45]. Most of these peptides and proteins are expressed on the tumor cell surface and are classified as tumor-associated antigens (TAA). Other emerging targets are the cancer-testis antigens (CTA), which are expressed in a wide range of cancer types. In contrast, their expression in normal tissues is restricted to immune privileged sites such as testis and placenta [46]. Some of these peptides and proteins are ideal targets for cancer-specific immunotherapy.
Collective excitations in α-helical protein structures interacting with the water environment
Published in Electromagnetic Biology and Medicine, 2020
Vasiliy N. Kadantsev, Alexey Goltsov
In the present paper, we further developed the quantum dynamic model of the collective excitations in α-helical protein structures (Davydov 1977), (Kadantsev et al. 1987; Lupichev et al. 2015), (Takeno 1984). We extended this approach to taking into account the dynamics of the side-chains which is suggested to be responsible for the protein interaction within the environment and modulation of the internal dynamics of the PG chain. In the model, a side-chain-dependent coupling of the vibration excitations in the PG chain and surrounding hydrogen bond network of water molecules was considered. The model development was based on a series of approximations which are either the typical ones in the theoretical modeling of molecular chains or based on the experimental data on protein dynamics. The parameters of the model were extracted from experimental data on the structure and strength properties of peptide bonds of the α-helix.