Characterization Of The Aggregated Patterns Of Three Surfactants Using Solvent Paramagnetic Relaxation Enhancements

Surfactants have been widely used in cleaning or hygiene produces,and chemical or biology sciences.The aggregation characterizations of surfactants are key properties underlying their application,which have been widely studied.however,the detailed aggregated parttern of a lot of micelles are usually controversial and uncertain,because of the lack of the high resolution.solvent Paramagnetic Relaxation Enhancements(sPRE)is obtained from soluble and freely diffusing agents.In this thesis,we analyzed the aggregation patterns of serveral surfactants(CHAPS,a zwitterionic surfactant,TX100,a nonionic surfactant and SDS,an anionic surfactant)by 1H sPRE experiments,in which Gd(DTPA-BMA)has been used as the paramagnetic probe.The results are as follows.1.The aggregated pattern of CHAPSCHAPS(3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate)is a typical zwitterionic detergent widely used in protein purification,which has two peculiar aggeration state.Using 1H Γ2u of CHAPS,sPREs produced by unit paramagnetic probe concentration,it was found that the 1H Γ1us of the zwitterionic tails of CHAPS are obviously bigger than those of the steroid head groups in both micellar states,and all of them become smaller simultaneously when the concentration of CHAPS is above CMC2.In addition,the Γ1us of those protons in the steroid ring are found to be very similar to each other in both micellar states.These results indicate that the micellar core of CHAPS is mainly formed by the steroid heads which aggregate disorderly.On the other hand,by futher analyzing of the Γ1us,it was found that a transition from single to double layer micelle is most likely to happen when the concentration of CHAPS is above CMC2.The micelles in second micellar state are formed by the aggregation of the partially disordered primary ones as well.Furthermore,the STD(Saturation Transfer Difference)experiment showed that the saturation transfer from water molecules to the protons near the hydroxyl group at the steroid head of CHAPS can be found in both micellar states.Whereas,the apparent coherence transfer rates between water and those protons near OH at the steroid head are slower in M1 state than those in M2 state,revealing that the CHAPS molecules aggregate loosely in M1 state,but more tightly in M2 state and water molecules insert into the micelles in the both micellar states.2.The aggregated pattern of TX100TX100(Triton X-100)is a typical nonionic surfactant that have been widely used in biology.Using 1H r2u of TX100,sPREs produced by unit paramagnetic probe concentration,it was found that the 1H ΓZus of the TX100 molecules become smaller from those of the hydrophilic polyoxyethylene moiety to those of the hydrophobic octylbenzene group,indicating that the TX100 molecules linearly inserted into the micelles.Compare with the Γ2u profile in monolayer layer spherical model,the Γ2u of different protons are more consistent with that in the multilayer staggered spherical micelle model with the p-tertoctylphenyl groups dispersing in the different layers.3.The aggregated pattern of SDSSodium dodecyl sulfate(SDS)is an anionic surfactant used widely in cleaning,hygiene products and biochemical analysis.To investigate the conformation of the Hydrocarbon chains in SDS micelles,13C Γ1u,of SDS,sPREs produced by unit paramagnetic probe concentration has been applied.The results show that the Γ1u of the 13C nucleus tend to become smaller from the polar ion head to the non-polar ends,indicating that the micelle core is assembled by the non-polar moieties of SDS moleclues.Further analysis shows that the relative Γ1us of 13C in different positions coincide with that deduced by onion aggregation model,in which the hydrocarbon chains fold deeply in each layer of the micelles.