Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

The air–lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air–liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C).     

Characterization of nutritional parameters in bovine milk by Raman spectroscopy with least squares modeling

The macronutrient constitution of bovine milk was investigated by Raman spectroscopy involving 830 nm excitation at 300 mW from 600–1800 cm^?1 with a probe. Bovine milk was analyzed for total proteins, casein, total fat, and lactose by standard assays. The concentrations of these components were estimated by correlating these assays with the fitting coefficients based on least-squares fitting of lactose, casein, triolein, and stearic acid and milk spectra to prepare calibration curves. The model was employed for the analysis of milk from local markets. The spectra of milk were dominated by bands of proteins, lipids, and carbohydrates. There was a strong correlation between the concentrations of total proteins and casein (r = 0.75 and 0.73, respectively), and very strong correlation for total fat and lactose (r = 0.93 and 0.91, respectively) with the standard errors of prediction of 0.49, 0.38, 0.61, and 0.27 mg/dL, respectively. The milk contained lower concentrations of lactose and protein than in the nutritional facts table. The amount of saturated fat was close to the nutritional value with more unsaturated fat. A single Raman spectrum was employed to characterize the composition of milk and may have application for rapid quality control.     

近红外光谱分析技术测定溶剂油芳烃含量

选取较长的一段时间内溶剂油生产装置中的样品100个，收集光谱，采用一阶微分和多元散射校正方法对光谱进行预处理，建立溶剂油芳烃含量的近红外光谱分析模型，并应用该模型对多种类型原油的溶剂油产品芳烃含量进行分析预测，将其结果与实验室色谱仪分析结果进行比较。实验的结果证明，用近红外光谱分析模型对未知样品进行预测的结果完全能够满足生产工艺中对精确度和重现性的要求，并能够满足工艺上对质量指标进行快速分析的要求。     

Atomic force microscopy study of chromosome surface structure changed by protein extraction

We applied atomic force microscopy (AFM) to investigate the surface structure of barley chromosome in combination with a chemical treatment method. As a result, we have obtained high-resolution topographic images of granular structures with a diameter of ca. 50 nm on the surface of critical-point dried metaphase chromosomes. Treatment with 2M NaCl significantly modified the chromosome surface structure: surface roughness was increased and chromosome thickness was decreased. The NaCl treatment extracted two major proteins with molecular weights of 4000 and 20,000 Da. These proteins might be belonging to non-histone protein families that do not contain any aromatic amino acid. The results demonstrate the advantage of the combined method of high-resolution AFM imaging and chemical treatments for understanding nano-scale surface structures of the chromosome.     

Measurements of polyphosphoric acid on HOPG

As a sample for initial study on biological materials by using scanning tunnelling microscope (STM), we selected phosphoric acid consisting of phosphorous atoms which play biologically an important role. We measured polyphosphoric acid coated on HOPG by STM and scanning tunnelling spectroscopy (STS) in air. In order to identify molecules on STM images, local I-V curves were taken simultaneously. The averaged I-V curves and the normalized conductance spectra of graphite coated with the acid show characteristics different from those of clean graphite surface. Around a step of the substrate, we found domains where normalized conductance spectra were different from those of clean graphite surface and ascribable to that of the adsorbed molecules.     

Electrospray: From ions in solution to ions in the gas phase,what we know now

There is an advantage for users of electrospray and nanospray mass spectrometry to have an understanding of the processes involved in the conversion of the ions present in the solution to ions in the gas phase. The following processes are considered: Creation of charge droplets at the capillary tip; Electrical potentials required and possibility of gas discharges; Evolution of charged droplets, due to solvent evaporation and Coulomb explosions, to very small droplets that are the precursors of the gas phase ions; Production of gas phase ions from these droplets via the Ion Evaporation and Charge residue models; Analytical uses of ESIMS of small ions, qualitative and quantitative analysis; Effects of the ESI mechanism on the analysis of proteins and protein complexes; Determination of stability constants of protein complexes; Role of additives such as ammonium acetate on the observed mass spectra. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:898–917, 2009     

Structure determination of tubular crystals of membrane proteins. III. Solvent flattening

Solvent flattening is considered to be a principal means for improving the data quality in X-ray crystallography. It could be equally effective for tubular crystals of membrane proteins imaged by electron microscopy because of the large empty space inside the tubes. However, tubular crystals are difficult objects for solvent flattening due to lack of electron diffraction amplitudes. Therefore, solvent flattening was used to align images more accurately and to improve the completeness of the data by reducing contributions of noise in the solvent (+ lipid) region. The methods developed were tested with the tubular crystals of Ca2+-ATPase embedded in amorphous ice. The improvement of the data quality was remarkable when solvent flattening was applied to many individual images before averaging. In this way, noises contaminated in the protein region by contrast transfer function were removed effectively. Solvent flattening was far more powerful than simple averaging described in Part II of this series (K. Yonekura, C. Toyoshima, Ultramicroscopy 84 (2000) 15).     

轮廓法测量残余应力中影响切割质量的参数研究

针对轮廓法测量残余应力的特殊要求,通过Plackett-Burman结合正交试验方法,揭示了线切割参数对轮廓法切割质量的影响规律,获得了对测量精度影响较大的三个因素:送丝速率、丝张力和峰值电流。方差分析的结果表明,较小的峰值电流和较大的丝张力有助于改善切割质量通过Box-Behnken响应面分析法,获得了表面粗糙度的预测模型,验证试验显示误差在5.011%以内,证明了该预测模型的有效性。     

小尺度摩擦副润滑特性数值模拟研究

与一般大型机械设备中的摩擦副不同,小尺度摩擦副润滑油膜在表面张力的作用下不再是水平形状,从而影响到摩擦副的摩擦学特性。在考虑到表面张力作用的基础上,对小尺度摩擦副进行摩擦学理论分析,建立了二维模型并求解了雷诺方程,以研究小尺度下表面张力对摩擦副摩擦学特性的影响。研究结果显示,由于表面张力的影响,摩擦副的油膜压力分布和承载能力有较大幅度的变化。宏观状态下的摩擦学设计与小尺度摩擦副的实际情况相去甚远,对小尺度摩擦副表面张力作用下的摩擦学特性进行研究是十分必要的。     

Latex on Glass: an Appropriate Model for Cartilage-Lubrication Studies?

Latex versus glass has frequently been used as a model system for the investigation of natural lubrication mechanisms, despite its significant differences from articular cartilage pairings. The differences in surface chemistry account for its different behavior in terms of protein adsorption and lubrication. While cartilage is well known for its protein resistance, most proteins present in synovial fluid can non-specifically adsorb onto latex or glass. We have investigated latex-versus-glass lubrication by means of pin-on-disk tribometry in the presence of synovial-fluid proteins and glycoproteins, focusing on the influence of the glass-cleaning procedure on friction. In order to simulate the effects of possible contamination of glass in previous studies, both hydrophilic and hydrophobic glass substrates were tested. Albumin was shown to impair lubrication (in comparison to PBS) when latex was slid against both types of glass surface, whereas bovine synovial fluid (BSF) and alpha-1-acid glycoprotein (AGP) impaired the lubrication of latex versus hydrophilic glass and improved the lubrication of latex versus hydrophobic glass. Protein adsorption on the surfaces was monitored by means of fluorescence imaging and optical waveguide lightmode spectroscopy (OWLS), which revealed a faster and greater amount of adsorption of AGP on hydrophobic surfaces than on hydrophilic ones. The influence of surface chemistry on the friction behavior of BSF and on the adsorption of AGP suggests that it plays a role in determining the relative amounts of adsorbed synovial fluid proteins. When BSF is used as a lubricant in the latex-versus-hydrophobic-glass system, more of the AGP, relative to albumin, appears to adsorb on both surfaces, counteracting the negative effect of albumin on friction. It therefore seems that latex on glass, while displaying nominal similarities to cartilage on cartilage under certain conditions, is not a useful model system. Moreover, surface contamination of the glass can play a major role in determining the results.