生物分离工程-双语版-7讲课教案.ppt
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1、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 grou
2、p 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 concen
3、tration,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 st
4、ate 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 g
5、lobular 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 deso
6、rption 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 prot
7、ein 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
8、 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 rest
9、orativesUnderstanding 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 adsorptio
10、nv1 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 tens
11、ion 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 i
12、n 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
13、 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 monol
14、ayer 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-protei
15、n 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(
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