生物分离工程-双语版-7讲课教案.ppt

生物分离工程-双语版-7Some parameters of influencing proteins-surface interaction v1 Electrostatic interactionsv2 pHv3 Surface chargev4 Co-adsorption of low-molecular weight ionsv5 Isoelectric pointv6 Intermolecular forcesv (1)molecules-moleculesv (2)solvent-solvent interactionv (3)strength of functional group bondsv (4)chemistry of solid surface and morphology v Proteins in solution diffuse to interface v1 Thermodynamically favorable processv2 Conformational hydration energy lost at interface.v3 Initially,at low protein concentration,no barrier adsorption,v diffusion controlledv4 At high surface concentration,activation energy barrierv adsorptionv(1)Electrostatic (2)Stericv(3)Osmotic effect close to the interfacial or surface layersv(4)Rearrange at surface is rate determiningvAdsorption of proteins at interfacev1 Proteins at gas-liquid interfaces are in an unfold v partially active or inactive state v (1)Conformational stability of flexible segmentsv (2)Interfaces are primarily responsible for protein v inactivation v (3)Shear-associated damage is severe at gas-v liquid interfacev A pumpv B centrifugesv C ultrafiltration Adsorption of proteins at interface 2 Proteins undergo a change from globular conformation to an extended chainv3 Adsorption of proteins-enzyme at interface is a complex v phenomenonv (1)transport to the interface by diffusion,convection,mixing v and shearing actionv (2)adsorption-desorption at interfacev A interfacial chemical reaction v B kinetic adsorption and desorption mechanismsv (3)structural change of molecules in contact with interfacev (4)adsorption competition between molecules of different v nature or molecular weight Factors of influencing protein adsorption onto surfacev1 Protein adsorption kineticsv2 Chemical equilibrium between interfacial v protein and solution proteinsv3 Flow of protein past adsorbing surfacev4 Conformation of proteins in the adsorbed v layerExample 7.1 v1 Some positive influence or consequences v (1)stabilization of microemulsion,pharmaceutical creams,v lotions,formulated foods and foamsv (2)protein purification strategy developmentsv (3)drug delivery systemsv (4)biosensors v2 Some negative aspects of protein adsorptionv (1)thrombus development on blood vessels and in artificial v implant materialsv (2)fouling of kidney dialysis membrane and in processing v equipmentv (3)plaque（饰斑）formation on teeth and dental restorativesUnderstanding proteins adsorption(1)structural rearrangements in protein molecule(2)redistribution of charged groups in interfacial layer(3)protein surface polarity(4)dehydration of sorbent surfaceII Adsorption of proteins and other biological macromolecules vA.Surfaces for protein adsorptionv1 An excellent protein-resistant surface adsorption-PEOv (1)Steric stabilization effectv (2)Van der Waals attraction is small compared with steric v repulsionv (3)Weak hydrophobic interaction between the PEO layer and v proteinv 2 Sedimentation volume method(Vsed)to characterize the v surface tension of protein-precoated polymer particlesB Monolayer adsorptionvMechanism of protein adsorption to surfacev(1)Attachment of different amino acid residues to surface (2)Interface will initially accommodate protein molecules that have the largest diffusion rate coefficient and most abundant present in solution.v(3)Initially adsorbed protein molecules may be displaced by v other protein with higher affinity.v(4)Isotherm(A langmuir,B Freundlich,C Henrys law)v(5)Many adsorption systems is represented by monolayer v adsorption systemsv(6)Second and higher layer are formed primarily by interaction v between molecules of the liquid mixture themselves.Example 7.3 Quantitative and qualitative featuresv1 Adsorption process was monitored by reflectometry v and by streaming potential measurementsv2 Sequential and competitive adsorption amount from v flowing solutions never exceeded values of v monolayer coverage(1-2ng/m2)v3 The effects of molecular size and diffusion v coefficient on adsorption preference are practically v negligiblev4 Hydrophilic surface adsorption is largely determined v by electrostatic interaction Hydrophilic surface adsorption (1)Protein amount adsorbed from single-protein solution increases with increasing charge (2)Sequential adsorption occurs only if the second protein has a more favorable electrostatic interaction (3)The final composition of adsorbed layer essentially consists of the protein that has most favorable electrostatic interaction with the adsorbent.v(4)Initial adsorption rate stages are not significantly affected v by the nature of the surface,at later stage,surface v becomes crowded with protein molecules and v result in heterogeneityv(5)At hydrophobic surface,electrostatic interaction v definitely do not dominate adsorption processSurface reaction of protein adsorption v1 An exchange reaction takes place in protein v adsorptionv2 Long protein molecule resides forms all its v possible bonds with a surface result in v conformation change and stronger bondsv3 Three types of protein surface adsorption v(1)Exchange reaction and reversible adsorption v takes place with small conformation changev(2)Only exchange reaction occursv(3)At least one kind of protein molecule is irreversibly v adsorbed on the surfaceThermodynamics of protein adsorption v1 longer the polar chain,the greater the endothermic valuev2 Protein chain increase H changes from v exothermic to endothermic at higher degrees of coveragev3 Dispersion component and surface energy determine protein v adsorptionv4 The lowering of the free energy is the driving force and gives v rise to the unfolding of the molecule at the surfacev5 Desorption isotherm shows a hystersis curve and does not v follow the adsorption curve.Thermodynamics of protein adsorption v Thermodynamic driving forcev (1)two positive entropic contributionsv A an entropy gain due to dehydration of protein v surfacev B an entropy gain due to adsorptionv (2)Two enthalpic effectsv A positive one associated with dehydrationv B a negative one due to interactions with the v solidv (3)Total entropic effect dominates and protein v adsorption is entropically driven D Adsorption parametersv1 Electrostatic interactionv2 Isoelectric point(maximum protein adsorption v around the isoelectric pointv3 pH (pH values away from the isoelectric point of v protein will increase electrostatic repulsion leads to v a smaller amount of adsorged proteinv4 Negatively charged surface(negatively charged v BSA molecule has a higher affinity for the negatively v charged polystyrene surfacev5 Surface charge D Adsorption parametersv6 Coadsorption of low molecular ionv7 Intermolecular force v8 Solute-solvent interaction,strength of v functional group bonds v9 Chemistry of the solid surfacev10 Morphologyv11 TopologyIII heterogeneity in protein adsorptionv1 Heterogeneity of surfacev (1)Significantly influence adsorption and reaction on v surfacev (2)Influence the rate and extent of protein denaturationv2 Heterogeneity influence protein adsorption v (1)Heterogeneity in solutev (2)Heterogeneity on surfacev (3)Models incorporating Heterogeneityv (4)Implications of this heterogeneity on protein adsorption and v reactions on the surfacev3 Distribution model of thermal activation energy for v deactivation IV Techniques for qualitative characterization of protein adsorptionvA Ellipsometry vMake more quantitative information about adsorbed protein films v(1)Thickness v(2)Refractive indicesv(3)Specific amountB Total internal reflection fluorescencevApplication v(1)Flowing solutionv(2)Measure adsorption kineticsv(3)Relating TIRF fluorescence signals to v protein surface concentrationsv(4)Examine initial adsorption,desorption and v exchange kineticC protein fluorescence and circular dichroism v1 Far-UV circular dichroism spectrav Only minor change in the protein secondary v structurev2 Intrinsic fluorescence v Reveal tertiary structure levelv3 Low-angle X-ray and neutron-scattering v technique v4 Enzyme methodC Probabilistic analysis for protein adsorption v1 Langmuir isotherm only is a macroscopic v characteristicsv2 A stochastic（推理的）approach is capable of v providing more details about a dynamic systemv3 Statistical analysis model the transient behavior of v reversible adsorption of small particles on a sold v surfacev4 Estimate both the mean and the fluctuating v characteristic of adsorption in a straightforward v mannerVI Conclusions v1 Heterogeneity influence initial protein adsorptionv2 Heterogeneity influence subsequent reaction v on the surfacev3 Heterogeneity does existv4 Protein adsorption lead to conformational change v and change of reaction ratev5 Very few models for protein adsorption define an v appropriate heterogeneity parameter and can relate v experimental resultsQuestionsv1 Which positive and negative effects for protein v adsorption at surface?v2 Why PEO is an excellent protein-resistant surfactant?v3 Why hydrophilic surface(SiO2)adsorption is largely v determined by elecrostatic interaction?v4 Which parameter affect protein surface adsorption?v5 Which techniques used for qualitative v characterization of protein adsorption?v6 Which undesirable property hydrophobic adsorbents v have?此课件下载可自行编辑修改，仅供参考！此课件下载可自行编辑修改，仅供参考！感谢您的支持，我们努力做得更好！谢谢感谢您的支持，我们努力做得更好！谢谢