111505 - BE.342/442 Tuesday, November 15, 2005 Topics...

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BE.342/442 Tuesday, November 15, 2005 Topics (guest lectures): (1) Macromolecular Interactions and Protein and Adsorption (2) Crystallography (1) Larry Unsworth, Ph.D., Associate Research Office, National Institute for Nanotechnology Objective: Presentation of general theory for macromolecular interactions. Specific examples of polymer and protein absorption. Intermolecular and macromolecule-surface interactions are ubiquitous in nature and control most biological events. E.g., thrombosis, hemostasis, cell-biomaterial interactions, gene transcription, protein translation, etc. Example of RNA translation: highly controlled selection to add amino acids to a peptide one at a time. Selective, specific interactions. Nonspecific protein adsorption is not selective. Use of biomaterials in medical applications can cause protein adsorption, leading to inflammation, thrombogenesis, hydrolytic and oxidative processes, and bacterial adhesion and growth. In fact, venous prostheses cannot be made at all due to almost spontaneous protein adsorption, and other prostheses in the circulatory system can lead to deadly coagulation. Interface: a region of a system in which there is an abrupt change of properties with distance. Interfacial phenomena direct macroscopic events, such as catalysis and bioactive species separation. Thermodynamics of adsorption Bulk solution ⇓⇑ native state vicinal state solute concentration and water structure differ from the bulk ⇓⇑ s p r e a d i n g initial attachment : multiple contact points =====SURFACE===================================
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In a homogeneous multicomponent system, all extensive properties can be related by U = U(S,V,N i ,…N r ,Q) U S V , N i , ..., N r , Q T U V S , N i , ..., N r , Q ≡− P U N i V , S , Q µ U Q S , N i ,..., N r , V F j Where U is the internal energy, V is the volume, N i is the number of moles of species i, S is entropy, and Q is charge. We can focus in on the internal energy of a surface by assuming zero volume and zero moles on the interface. The intensive variables are defined as the partial derivatives of the internal energy with respect to their conjugate extensive variables, with all other variables held constant. This is how we define the interfacial surface tension γ LV , interfacial chemical potential µ i LV , interfacial surface temperature T LV , and interfacial electrical potential φ LV . The differential form of the interface internal energy can then be written for a liquid-vapor interface as the Gibbs dividing surface equation: dU LV = T LV dS LV + γ LV dA LV + Σµ i LV dN i LV + φ LV dQ LV Rearranging, we obtain the Gibbs Absorption Equation: γ LV = -SdT LV - ΣΓ i d µ i LV - q LV d φ LV Here, Γ is the surface fraction due to non-adsorbed chains. The total entropy of the system is the sum of the entropies of the liquid phase, the vapor phase,
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This note was uploaded on 11/11/2011 for the course BIO 20.410j taught by Professor Rogerd.kamm during the Spring '03 term at MIT.

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111505 - BE.342/442 Tuesday, November 15, 2005 Topics...

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