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Unformatted text preview: 4. Peptide bond formation II. Peptides A. Peptide Bond Formation 1. Condensation reaction 2. Residue: single amino acid 3. Polypeptide: 10-100 amino acids 4. Protein: more than 100 amino acids B. Molecular Weights 1. Average MW of amino acid=110 2. MW of proteins = 220-220,000 1 amu = 1 dalton C. Termini 1. Amino (N-terminus) 2. Carboxyl (C-terminus) D. The chemical and physical properties of proteins depend on their amino acids. 1. Determining net charge at a given pH a. Use pKa values to obtain charges on side chains b. Include charges at termini c. add charges 2. Microenvironment can affect properties of nearby side chains 3. Isoelectric point (pl) = pH when molecule has no net charge E. Physiologically Active Peptides 3aa 1. Glutathione -scavenger for oxidizing agents 5aa 2. Enkephalin - brain (pain relievers) 3. Oxytocin - contraction of uterus : milk flow 9aa 4) Vasopressin - blood pressure...
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