| Aimed at the study on interface interaction between high-silicon-calcium ultrafine mineral granule and common bacteria and its cell wall- membrane components, in this paper, several typical granules were chosen as particulate matter, such as quartz(KWC-Q), montmorillonite(KWC-M) and calcite(KWC-C) with their particle size of 2.5 ?m, and nanoparticles Nano-Si O2, Nano-Ca CO3; and we chose the content of cell wall/membrane as biomolecule. E. coli and Staphylococcus epidermidis were chosen as represented microbe strains. Different interaction system of IMG-biomolecules/ common bacteria was built. The interface interaction between high-silicon-calcium ultrafine mineral granule and common bacteria as well as its cell wall-membrane biomolecules was studied through fluorescence spectra, ATR-FTIR(attenuated total reflectance Fourier transform infrared spectroscopy), XRD(X-ray diffraction), XPS(X-ray photoelectron spectroscopy) and SEM(scanning electron microscope), and so on. The research results were mainly focused on the biomolecular fluorescence quenching, change of the functional groups, structure and morphology change, etc. The results were showed as below.In the interface adsorption process of amino acids adsorbed onto montmorillonite, the results of XPS and ATR-FTIR showed there were electrostatic attraction between the-NH3+ group and the structural negative charge, Al OH2+ of montmorillonite and — COO—group. In the dissolution process of high-silicon-calcium ultrafine mineral granule, the Ca dissolving amount of KWC-C in amino acids showed Glu > Ala > Trp > Val > Gly > Lys; and the Si dissolving amount of KWC-Q in amino acids showed Lys > Gly > Val >Ala > Trp > Glu.The fluorescence intensity of protein was reduced caused by the mineral sample, resulting in the fluorescence quenching effect of BSA(bovine serum albumin). The result of Stern- Volmer equation showeded the mechanism of fluorescence quenching was a combination of dynamic and static quenching mechanism. Dynamic quenching was caused by particles colliding with protein molecules. In the process of static quenching, the binding sites n of Nano-Si O2 and Nano-Ca CO3 with BSA at 283.16 K and 313.16 K were 1.010, 1.221, 0.6882 and 1.221 respectively, nearly equal to 1. That is to say, there was 1:1 type complex formed between NPs and protein molecule and the complex was non-fluorescigenic. ATR-FTIR result demonstrated that mineral particles caused reduction of ?-helix and ?-sheet that translated into ?-turn in the second structure of protein.The interaction result of mineral particles and peptidoglycan confirmed that the consumption of OH- in dissolution process of high-silicon ultrafine mineral promoted the alkali dissociation of amino acids in peptidoglycan tetrapeptide side chain, resulting the the protonation of —NH2 to form a positively charged groups —NH3+. And the dissolution process of high-calcium ultrafine mineral promoted the acid dissociation of tetrapeptide side chain. The results showed that the sdudied mineral particles resulted in the electron transition change of n??* and ???* in peptidoglycan molecules, causing UV absorption spectrum change at wavelength of 193 nm?197.5 nm and 202.5 nm. Interacted with the ultrafine mineral granules, the functional groups of peptidoglycan were greatly affected including the groups of secondary amide in disaccharides unit, –CH2– in the tetrapeptide side chain, ?as(C–O–C) in glucosidic bond at 1137 cm-1 and amide III, etc. Sometimes, it was only at high concentrations of KWC-C, the above group changes of peptidoglycan would appear. The group changes of peptidoglycan caused by ultrafine high-silicon mineral granules were stronger than the effect caused by high-calcium granules.The presence of phospholipids in Tris-HCl solution would promote the dissolution of high-silicon particles, but inhibit the dissolution of high-calcium ones, causing the reduction(high-silicon) or increase(high-calcium) of p H values at about 6.80 or 7.01. Under the liquid phase environment, the interaction between the mineral particles and carbonyl and carboxyl in humus caused the fluorescence intensity change of fulvic acid in the phospholipid molecules. And the fluorescence quenching rate caused by Nano-Si O2 was higher than that caused by the other several particles. Moreover, the liquidity of the phospholipid membrane was reduced mainly induced by Nano-Si O2 that can increase the vertical and horizontal ordering of the phospholipid molecules.In the interaction process of ultrafine atmospheric mineral granules and common bacteria cell wall and membrane, adhesion occurred between the bacteria and particles. At first, the functional group and structure changes of biological small molecules(such as amino acid, monosaccharide molecules) were caused by particles in the cell wall and membrane of common bacteria, and then the related biomacromolecules(peptidoglycan, lipopolysaccharide, protein and phospholipid, etc.) were also affected including fluorescence quenching, molecular conformation change and the change of surface functional groups, causing structure damage of the biological macromolecules. Because of the structure destruction, the common bacteria showed surface depression, shrinkage or even collapse, cell rupture and intracellular substances flowing out of the cell, finally the bacteria cells died. Of course, after interaction with the common bacteria, the lattice and surface functional groups of the studied mineral particles have also been changed to a certain degree. |
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