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lecture5 - 3.051J/20.340J Lecture 5: Protein-Surface...

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3.051 J / 20 .340 J 1 Lecture 5: Protein-Surface Interactions Importance of Protein-Surface Interactions: Modulate cell adhesion Trigger the biological cascade resulting in foreign body response Central to diagnostic assay/sensor device design & performance Initiate other bioadhesion : e.g., marine fouling, bacterial adhesion Fundamentals on Proteins: Largest organic component of cells (~18 wt% /H 2 O =70%); extra- cellular matrix, and plasma (7wt% /H 2 O=90%). Many thousands exist —each encoded from a gene in DNA. Involved in all work of cells: ex, adhesion, migration, secretion, differentiation, proliferation and apoptosis (death). May be soluble or insoluble in body fluids . Insoluble proteins —structural & motility functions; can also mediate cell function (ex., via adhesion peptides) Soluble proteins —strongly control cell function via binding, adsorption, etc. Occur in wide range of molecular weights .
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3.051 J / 20 .340 J 2 “Peptides” (several amino acids): hormones, pharmacological reagents e.g., oxytocin: stimulates uterine contractions (9 a.a.) aspartame : NutraSweet (2 a.a.) “Polypeptides” (~10-100 amino acids): hormones, growth factors e . g . , insulin: 2 polypeptide chains (30 & 21 a.a.) epidermal growth factor (45 a.a.) “Proteins” 100’s-1000’s of amino acids e . g . , serum albumin (550 a.a.) apolipoprotein B: cholesterol transport agent (4536 a.a.) Protein Functions: Structural/scaffold : components of the extracellular matrix (ECM) that physically supports cells e.g., collagen —fibrillar, imparts strength; elastin —elasticity to ligaments; adhesion proteins : fibronectin, laminin, vitronectin —glycoproteins that mediate cell attachment (bonded to GAGs) Enzymes : catalyze rxns by lowering E a thru stabilized transition state, via release of binding energy e.g., urease —catalyzes hydrolysis of urea
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3.051 J / 20 .340 J 3 Transport : bind and deliver specific molecules to organs or across cell membrane e.g., hemoglobin carries bound O 2 to tissues; serum albumin transports fatty acids Motile : provide mechanism for cell motion e.g., via (de)polymerization & contraction e.g ., actin, myosin in muscle Defense : proteins integral to the immune response and coagulation mechanism e.g., immunoglobulins (antibodies) —Y-shaped proteins that bind to
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lecture5 - 3.051J/20.340J Lecture 5: Protein-Surface...

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