In the UV-Vis spectra of pure light-scattering systems, there is an exponential relationship between absorbance and wavelength (A = Kλ-n). Here, the exponent n is named as flocculation-coagulation parameter. In the present paper, the effects of different additives on the stability of poly(N,N'-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP))microgel dispersion were studied in detail via this parameter. The results showed that the stability of the dispersion mainly comes from the ionization of pyridine groups, making the microgel positively charged on its surface. This was confirmed by the measurement of Zeta potential and the result of conductometric titration. The result of fluorescence analysis indicated that the hydrophobicity in the microgels is enhanced with the increase in total 4-VP unit content.
The effects of L-phenylalanine (L-Phe) on the synthesis ofpoly(N,N'-methylenebisacrylamide-co-4-vinylpyridine)(poly(Bis-co-4-VP)) (micro)gels by T-ray irradiation were studied. The addition of L-Phe could not only decrease the gelation dose (Dg) of the synthesis obviously, but also transform the morphology of copolymer from microgel to gel. In addition, the swelling ability of the (micro)gels was also affected in the presence of L-Phe. The decrease of Dg was ascribed to the effect of pH, while the transformation of the morphology was ascribed to the effect of L-Phe on the stability of the poly(Bis-co-4-VP) microgel. Such an effect was confirmed further as compared with the effects of L-alanine, L-glutamic acid, L-arginine, sulfuric acid and aqueous ammonia.
The binding between three surface-active substituted 3H-indole fluorescence probes and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence quenching. The binding constants of 3H-indole molecules with BSA were obtained. According to the F?rster resonance energy transfer theory, the distances between 3H-indole molecules and tryptophan of BSA were calculated. The results show that the oligoethyloxyethylene chain of 3H-indole molecules is longer, the binding between them is stronger, the energy transfer efficiency is higher, and the distance between tryptophan and 3H-indole is nearer.
The study of cyclodextrin nanotubes is a significant topic among the self-assembly behaviors of cyclodextrins.We report herein the interaction of 2,5-bis(5'-tert-butyl-2-benzoxazoyl)thiophene(BBOT) with α-,β-,γ-cyclodextrins(CDs).It has been discovered that the reaction patterns of BBOT with CDs are remarkably different.α-CD forms a simple inclusion complex with BBOT in a stoichiometry of 1:2(guest:host).β-CD forms a 1:1 inclusion complex with BBOT at its low concentration.At higher concentration of BBOT,the nanotube and secondary assembly of β-CD are formed.As for γ-CD,the nanotube and secondary assembly are formed within the whole concentration range of BBOT studied.The structure of γ-CD nanotubes is different from that of β-CD nanotubes to a certain extent.
ZHANG JingJing,SHEN XingHai,WU AiHua,ZHANG ChunFen,CHEN QingDe & GAO HongCheng Beijing National Laboratory for Molecular Sciences
