Study On Properties Of Molecular Recognition Of Polydiacetylene Functionalized With Glycolipid

Cell membranes are perfect structures from a materials science point of view. These highly organized, self assembly structures provide indispensable functions for cell such as molecular recognition, signal transduction and energy conversion. The design of smart artificial membrane with special function characteristic is an emerging field of research.In this thesis, we design a simple and direct method to detect molecular recogniton interactions. A series of glycolipid (MPDA 1-7) were synthesized, mixed with 10,12-pentacosadiynoic acid (PDA). The recognition of MPDA/PDA mixed LB films and vesicles on E.coli K12 was studied in detail. The bactericidal effect of nanoparticles of TiOi photocatalysist was tested by this directly chromatic method. The experiments show:Properties of MPDAi/PDA monolayer were greatly affected by pH value, temperature of subphase and mixed ratio of MPDAi and PDA. When subphase temperature is 14 ℃, pH is 5.6 and MPDAj.3, 5/PDA is mixed in a ratio of 1:20, the quality of the monolayer is better. But MPDA6-7 does not dissolve in common reagent, it can't be used in this work. The properties of MPDA 1-5 are studied in detail. MPDA 1-3 all can be recognized by E. coli K12, colorimatric response (CR) is 31%(MPDAi/PDA), and MPDA/PDA film changes color from blue to red. The absorption maxima at 640nm on UV-visible absorption spectroscopy of the film shift to 540nm. Comparing the chromatic properties MPDAs is better than other MPDA, and the background is low. This kind of chromatic molecular recognition is irreversible and specific. Kinetics of the recognition process was discussed. We estimate that Escherichia coli cell can only bindtwo MPDAs molecules. Mechanism of PDA chromatic response to molecular recognition was investigated by Raman spectroscopy.Chromatric properties of MPDAs / PDA (1:20 in volume) vesicles were studied. High quality of vesicles were prepared by sociating for 30 min at 72-76℃ and placing for 48 hours at 4℃ to make vesicles close. Comparing influence of the different dilution to the optical characteristic of vesicles, the results show that the change of salt water on UV-visible absorption spectroscopy is lowest. Kinetic experiments shown that the color change induced by the addition of an aliquot of E.coli reaches a plateau after 2min. Colorimetric response (CR) of vesicles at different concentration were calculated. The influence of different cation on molecular recognition was investigated in vitro. The results show: Cd2+> Ca2+> Ba2+> Mg2+> Fe3+> Cu2+. Fe3+, Cu2+ can inhibit the recognition, and the exist of Ba2+or Mg2+ does not influence the recognition, but the exist of Cd2+ or Ca2+ can improve the molecular recognition or increase colorimetric degree of vesicles. Especially Cd2+, the colorimetric response is double. The binding of vesicles on E.coli was characterized by FTIR and Raman spectroscopy.Bactericidal effect of colloid TiO₂ was detected by directly chromatic method. Neutral colloid TiO₂ was prepared, we have found that a suspension of E.coli K12 and colloid TiO₂(l:4) were pre-incubated for 1 h, and irradiated for 1 h (UV 365nm), all of bacteria were killed (CR is to 6.6%, which is equal to background). The colloid TiO₂ we prepared is a stronger photocatalysis disinfectant.Finally, cyclic voltammetric method was used to detect the molecular recognition of E.coli K12 on mannose in polydiacetylene derivative supported on the self-assembled monolayers of octadecanethiol on a gold electrode. After the electrode was incubated with E.coli K12 for 3min, the peak current gradually decreased and appeared plateau-shaped at potential past the redox potential of probe molecules and the current decreased exponentially after 5min. The amperometric signal decreased quickly with increasing concentration within the range of Ixl08 to 7x108 cells/mL. These changes were attributed to the decrease of defect density within the bilayer of MPDA2/PDA.