Automated identification of amino acid sequence variations in proteins by HPLC/microspray tandem mass spectrometry

Amino acid sequence variations resulting from single-nucleotide polymorphisms (SNPs) were identified using a novel mass spectrometric method. This method obtains 99+% protein sequence coverage for human hemoglobin in a single LC-microspray tandem mass spectrometry (microLC-MS/MS) experiment. Tandem mass spectrometry data was analyzed using a modified version of the computer program SEQUEST to identify the sequence variations. Conditions of sample preparation, chromatographic separation, and data collection were optimized to correctly identify amino acid changes in six variants of human hemoglobin (Hb C, Hb E, Hb D-Los Angeles, Hb G-Philadelphia, Hb Hope, and Hb S). Hemoglobin proteins were isolated and purified, dehemed, (S)-carboxyami-domethylated, and then subjected to a combination proteolytic digestion to obtain a complex peptide mixture with multiple overlaps in sequence. Reversed-phase chromatographic separation of peptides was achieved on-line with MS utilizing a robust fritless microelectrospray interface. Tandem mass spectrometry was performed on an ion trap mass spectrometer using automated data-dependent MS/MS procedures. Tandem mass spectra were collected from the five most abundant ions in each scan using dynamic and isotopic exclusion to minimize redundancy. The spectra were analyzed by a version of the SEQUEST algorithm modified to identify amino acid substations resulting from SNPs.     

Gap measurement by position-sensitive detectors

A system for measuring the gap in a proximity exposure tool of a plasma display panel (PDP) is developed that uses single or dual position-sensitive detectors (PSD's). The resolution of the gap distance is 0.5 mum, with a capture range of 500 mum. Signal processing is simple and fast and easy because analogous PSD's are used as the position sensors. One PSD is used to detect the position of the reference beam, which is reflected from the upper surface of the gap; the other PSD is used to detect the position of the signal beam, which is reflected from the lower surface of the gap. A charge-coupled-device sensor is also employed to monitor the reflected beams and the region of measurement. In the gap-measurement system that uses a single PSD, first the reference beam is incident upon the PSD and then the signal beam is incident upon the same PSD. Then the separation between the two beams is calculated from the position of the reference beam and from the average beam position.     

300MW引进型机组控制系统的DEH改进

介绍了引进型３００ＭＷ汽轮机组控制系统ＤＥＨⅡ型和ＤＥＨⅢ型的比较，指出了ＤＥＨⅢ型控制系统比ＤＥＨⅡ型具有更好的先进性、可靠性、安全性和灵活性，对火电机组安全经济运行     

How dry are dried samples? Water adsorption measured by STM

When operating scanning probe microscopes, like STM or AFM, under ambient conditions, the presence of water on the sample and the tip always plays an important role. The water not only influences the structure of the sample itself, but also the imaging process; in the case of the STM using a wet etched w-tip, by interfering with the electron transfer process, and in the case of the AFM, due to the capillary forces in the micro Newton range that dominate the tip surface interaction forces. In this paper, the distribution and the amount of adsorbed water on different surfaces is investigated with the help of the STM, which can provide information by imaging and by current/distance spectroscopy. Hydrophilic and hydrophobic surfaces like titanium, gold, and graphite were studied at a relative humidity between 10 and 90%. Under very dry conditions with relative humidity below 15%, the presence of water was only detectable by the longer decay length of the measured current with distance compared to samples prepared in UHV completely free of water. At less dry conditions on gold surfaces, water was found as droplets. With increasing humidity, the quantity and the size of these droplets increased until the whole surface became covered with water. Above 55% humidity, the thickness of the water film increased with increasing humidity up to several 10 nm. On titanium and graphite, water was always present in the form of closed layers growing in thickness with increasing humidity.     

Deep nulling of visible laser light

Nulling interferometry, a proposed technique for dimming a star relative to its surroundings by destructively interfering the light collected by two individual telescopes [Bracewell, Nature 274, 780-781 (1978); Shao and Colavita, Ann. Rev. Astron. Astrophys. 30, 457-498 (1992)], has the potential to permit the direct detection of nearby extrasolar planets. However, because of the extremely high degree of symmetry required for useful levels of starlight nulling, the technique remains in its infancy. We present results of laboratory experiments with a rotational shearing interferometer that are aimed at demonstrating the feasibility of deep nulling at the levels needed for direct planet detection. Our first results include the successful nulling of red laser light to a part in 10(5) and the stabilization of the null leakage to a part in 10(4).     

梯田控制侵蚀的投资与效益

本文引用美国1978年资料,估计修建梯田的投资,从农民的立场观点出发进行研究,论证修建梯田是否经济。在1-15％的斜坡土地上,研究并试验了坡道及排泄管道两种形式的梯田或地埂。修建梯田的政府投资部份,也进行了分析计算。对两种耕作管理水平和两种底层土壤形式,作为参数,进行研究试验。在伊林诺伊斯(Illinois)州,根据土壤原有的生产能力、可侵蚀性、底层土种类、坡度范围等,选择了一些普通土壤,应用土壤流失通用方程,估算各种情况下的土壤流失。采用1978年的谷类及豆类的价格,估算经济效益。研究分析指出:除少数情况外,农民愿意拿出部分生产收入,修建梯田,以控制土壤侵蚀。尽管这种研究分析结果,与效益的取得应与其他水土保持措施有关的意见相抵触,但应说明,我们的研究分析仅仅是估算修建梯田的直接效益。倘考虑其他侵蚀的投资,则修梯田的效益可以抵消其费用。至于为防止将来土壤流失所造成农业减产须促进水土保持,其所需增加的其他费用,理应由政府机构增加投资。在许多地方,土壤年年被侵蚀流失。每天有1200万吨沉积物流失,污染邻近48州的表层水质。这些流失的泥沙,损害了工程建筑物、农作物、野生植物。伊利诺斯州农业区的侵蚀量,每年超过1.81亿吨。在970万英亩的坡地中,只有14％适当地防治了侵蚀。控制侵蚀有很多措施,包括耕作制度或作物轮作。修造梯田也是一种控制侵蚀的有效措施,但修建梯田即使政府投资一部份,其费用也是昂贵的。这种昂贵的费用,妨碍了一些土地所有者对修造梯田的积极性。然而,让土壤被侵蚀无控制地发展下去,是要花代价的。土壤被侵蚀,最终将使产量降低、使下游河道淤塞、灾难造成。本文研究的目的,仅从农民的立场观点出发,论证修建梯田是否经济合理。我们是在伊利诺斯州几种坡道的土壤上,从土壤的生产能力、土壤的侵蚀性、底层土的种类、表土流失降低产量、耕作管理水平、以及修建梯田的投资等方面来进行经济合理的论证。     

Survey of shell egg processing plant sanitation programs: effects on non-egg-contact surfaces

To successfully implement a hazard analysis critical control point plan, prerequisite programs are essential. Sanitation standard operating procedures are an important part of such a plan and can reduce contamination levels so that food safety and quality are not adversely affected. Noncontact surfaces in the shell egg processing plants can serve as a reservoir of cross-contamination. The objective of this study was to assess the efficacy of sanitation programs used in a variety of shell egg processing facilities (in-line, off-line, and mixed operations). Fourteen different noncontact surfaces were sampled in nine commercial facilities across the southeastern United States. Non-egg-contact surfaces were defined as those where the shell egg does not come into direct contact with the surface or with the fluid from that surface. Gauze pads soaked in sterile phosphate-buffered saline were used for sampling at the end of a processing day (POST) and again the next morning prior to operations (PRE). Aerobic plate counts (APCs) and numbers of Enterobacteriaceae were determined. No significant differences (P > 0.05) were found between POST and PRE counts for either population recovered from the 14 sampling sites. Only samples from the floor under the farm belts, nest-run loader, washers, and packer heads were reduced by 1 log CFU/ml of rinsate for APCs or Enterobacteriaceae counts. APCs of more than 10(4) CFU/ml of rinsate were recovered from many samples. Highest APCs were found on the floor under the farm belt and on shelves of the nest-run carts. High APCs were found on the wheel surface for off-line carts and on the loading dock floor. Highest Enterobacteriaceae counts were found in samples from the floor, drain, and nest-run egg cart shelves. A lack of significant difference between POST and PRE counts indicates that current sanitation programs could be improved. These data suggest that traffic patterns for the movement of eggs and materials through the plant should be reevaluated so that cross-contamination is reduced.     

Screening for novel essential genes of Saccharomyces cerevisiae involved in protein secretion

We describe here a screening procedure devised for searching new genes involved in protein secretion in Saccharomyces cerevisiae. The screening procedure takes advantage of yeast strains constructed within the EUROFAN project, in which the promoters of the novel essential genes were replaced by the doxycycline-regulated tetO(7)-CYC1 promoter. This promoter is active in normal growth medium but results in downregulation of the gene in the presence of doxycycline. The yeast cells were grown in the presence or absence of doxycycline, and both the growth and secretion of the heat shock protein, Hsp150p, into the culture medium were determined. In seven strains there was a specific effect on protein secretion. In a strain in which the RPN5 gene was downregulated, the level of secreted Hsp150p was increased compared to the control culture. When RER2 was downregulated, cells secreted Hsp150p that was not of the mature size. In five strains, secretion was more severely reduced than cell growth. One of these downregulated genes, YGL098w, was recently reported to encode an ER-located t-SNARE, USE1. Four of the genes detected, NOG2, NOP15, RRP40 and SDA1, encode proteins involved in ribosome assembly, suggesting a possible new signalling pathway between ribosome biogenesis and production of secreted proteins. The results obtained here indicate that the present screen could be successfully used in larger scale to identify novel secretion-related genes.