lecture2 - 10.492 Integrated Chemical Engineering(ICE...

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Lecture #2 – Review of Protein Chemistry, Enzyme Specificity Handouts: (1) Structures of amino acid side chains, (2) Sample bioconversions to examine specificity 1. Review of protein chemistry, enzyme specificity Recall that proteins have a primary structure that is the string of amino acids as encoded by the DNA. There are twenty amino acids, of the general structure: R - OOC NH4 + H where R is the side chain. Side chains come in three “flavors”: hydrophobic, hydrophilic, and “other.” The extent to which side chains are hydrophilic or hydrophobic varies with each group (refer to handout). For example, the hydrophobic group contains both the branched chain aa’s valine and leucine, as well as the cyclic side chains of tryptophan and phenylalanine. The hydrophilic group contains the polar aa’s serine and threonine, as well as charged aa’s aspartic acid, glutamic acid, and lysine. The two classified as neither hydrophobic nor hydrophilic are cysteine (sulfur-containing) and proline. Proteins also have secondary , tertiary and quaternary structures. The secondary structure is defined by the local structure of the linear (primary) string of amino acids. Secondary structures are general in the form of α -helices, β -sheets, or flexible. The tertiary structure represents the higher-order folding of the chain into its final three- dimensional structure, while quaternary structures are formed from the interaction of two or more individually-folded chains. Proteins take on their predestined structure based on the nature of the amino acids of which they are comprised. They are held together in an active (or inactive) conformation through various, mostly weak forces, including hydrophobic interactions, electrostatic (ionic) forces, and hydrogen bonding. Keep in mind as well that proteins are typically found in aqueous environments, so the presence of water is a prime determinant in the ultimate configuration of any polypeptide chain. Why do we care about the nature of the protein structure and the forces that hold it
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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lecture2 - 10.492 Integrated Chemical Engineering(ICE...

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