Savinase action on bovine serum albumin (BSA) monolayers demonstrated with measurements at the air-water interface and liquid Atomic Force Microscopy (AFM) imaging

We studied the enzymatic action of Savinase on bovine serum albumin (BSA) organized in a monolayer spread at the air/water interface or adsorbed at the mica surface. We carried out two types of experiments. In the first one we followed the degradation of the protein monolayer by measuring the surface pressure and surface area decrease versus time. In the second approach we applied AFM imaging of the supported BSA monolayers adsorbed on mica solid supports and extracted information for the enzyme action by analyzing the obtained images of the surface topography in the course of enzyme action. In both cases we obtained an estimate for the turnover number (TON) of the enzyme reaction.     

针尖化学方法研究单壁碳纳米管末端羧基的解离性质

针尖化学利用化学手段对扫描探针显微镜 ( SPM)的针尖进行功能化修饰 ,将其作为化学反应的“探针”用于研究表面的局域化学反应性质、跟踪表面发生的化学反应过程等 [1] .用针尖化学技术来研究自组装膜 ( SAMs)表面酸碱基团的局域解离性质 ,称之为化学力滴定 [2～ 8] .利用表面缩合方法将单壁碳纳米管短管组装到 AFM针尖上 ,通过测定针尖上碳纳米管的末端基团与羟基自组装膜表面之间的粘滞力 ,研究碳纳米管末端羧基的解离性质 ,可得到碳纳米管结构与化学性质的信息 .1　实验部分1 .1　碳纳米管针尖和羟基末端自组装膜的制备　基底 [Si( …     

Rapid biosynthesis of silver nanoparticles from Bacillus megaterium (NCIM 2326) and their antibacterial activity on multi drug resistant clinical pathogens

The notion to fight against multi drug resistant pathogens is a great deal in the field of nanomedicine. The identifiable antimicrobial action of metal bionanoparticles on many microorganisms is reported earlier. As silver bionanoparticles (Ag-BNPs) are known to have efficient antibacterial properties they are synthesized in ecofriendly and biocompatible way. The present study is focused on the extracellular biosynthesis of highly stable Ag-BNPs from bacterial strain Bacillus megaterium (NCIM 2326) by bio-reduction of silver ion using the culture supernatant, and to determine the antibacterial efficacy on multi drug resistant clinical pathogens such as Streptococcus pneumoniae and Salmonella typhi. The biosynthesis process is rapid and Ag-BNPs are formed within few minutes if AgNO(3) comes to contact with cell filtrate. Furthermore the synthesized Ag-BNPs are characterized by UV-vis spectroscopy, Atomic Force Microscopy (AFM), Thin Layer Chromatography (TLC) and Fourier Transform Infrared Spectroscopy (FTIR).     

Tuning the properties of a black TiO2-Ag visible light photocatalyst produced by a rapid one-pot chemical reduction

A highly efficient black TiO₂-Ag photocatalytic nanocomposite, active under both UV and visible light illumination, was synthesized by decorating the surface of 25 nm TiO₂ particles with Ag nanoparticles. The material was obtained via a rapid, one-pot, simple (surfactant and complexing agent free) chemical reduction method using silver nitrate and formaldehyde as a metal salt and reducing agent, respectively. The nanocomposite shows an increase of over 800% in the rate of photocatalytic methylene blue dye degradation, compared to commercial unmodified TiO_2, under UV-VIS illumination. Unlike pure TiO₂, the nanocomposite exhibits visible light activation, with a corresponding drop in optical reflectance from 100% to less than 10%. The photocatalytic properties were shown to be strongly enhanced by post-reduction annealing heat treatments in air, which were observed to decrease, rather than coarsen, silver particle size, and increase particle distribution. This, accompanied by a variation in the silver surface oxidation states, appear to dramatically affect the photocatalytic efficiency under both UV and visible light. This highly active photocatalyst could have wide ranging applications in water and air pollution remediation and solar fuel production.