Crystallization and atomic resolution X-ray diffraction analysis of antichymotrypsin variants

Crystals of two recombinant antichymotrypsin (rACT) variants have been prepared: variant rACT-T345R crystallizes in space group P2(1) (a = 109.2 A, b = 79.4 A, c = 111.9 A, beta = 116.3 degrees, with 2 molecules in the asymmetric unit), and variant ACT' crystallizes in space group P2(1)22(1) (a = 69.7 A, b = 77.2 A, c = 83.8 A, with one molecule in the asymmetric unit). The latter variant is an engineered dimer having the P3-P3' hexapeptide sequence of the related serpin, alpha 1-proteinase inhibitor, substituted for the corresponding wild-type sequence. Crystals of each variant diffract to a limiting resolution of 2.5 A, which represents the best diffraction yet achieved for a crystalline, inhibitory serpin. The exceptional quality of ACT' crystals probably arises from favorable protein-protein interactions as well as a stabilizing disulfide crosslink engineered between the monomers.     

高分辨连续光源原子吸收光谱法测定钒铁中磷

由于P的共振线(178 nm)位于紫外真空区,直接用火焰原子吸收光谱法进行测定较为困难。而P在适宜比例的乙炔/空气火焰中,可产生一系列PO双原子分子吸收光谱,故可应用连续光源原子吸收光谱法对P进行定量分析。样品用硝酸和盐酸加热溶解完全后,在适宜比例的乙炔/空气火焰中以PO 327.04 nm为分析线,建立了高分辨连续光源原子吸收光谱法测定钒铁中P的方法。确定了高分辨连续光源原子吸收光谱仪的最佳工作条件为乙炔和空气流速比0.16,燃烧头高度12 mm,积分像素点9 pixl。实验表明:P质量浓度为5.0～80 mg/L范围内与其吸光度呈良好的线性关系,其线性方程为y=0.000 8 x+0.001 9,相关系数r为0.999 5。方法检出限为1.0 mg/L。样品中共存元素的干扰试验表明:基体元素V、Fe对测定P无干扰;Ca、Mg元素对P的测定虽有干扰,但样品中存在的Al因可以与Ca、Mg元素形成较为稳定的CaAl₂O₄和MgAl₂O₄化合物而消除了其干扰。采用实验方法测定钒铁标准物质和实际样品中P的测定,测得结果与认定值基本一致,相对标准偏差(RSD,n=11)为1.9%～4.4%。     

Mapping flexible protein domains at subnanometer resolution with the atomic force microscope

Eosinophils are emerging as an increasingly important cell in the immunoregulatory network of normal and pathological processes. No studies has yet described optimized experimental strategies to transfect DNA into human eosinophils. Using a frequently employed in vitro model of human eosinophil, the EoL-1 cells, we now described the optimal transfection of DNA into these cells by electroporation. Our results indicate that electroporation can efficiently and reproducibly transfect DNA into EoL-1 cells. Optimal electroporation conditions consist of the use of 1 X RPMI medium 1640 with 10% FBS, voltage setting at 275 V, 1150 microF capacitance, 40 mg of DNA and 4.0 X 10(7) cells/ml per electroporation in a total volume of 0.5 ml in 0.4 cm gap cuvettes. These conditions may be a useful protocol for transfecting eosinophil cell lines.     

Viscoelasticity of living cells allows high resolution imaging by tapping mode atomic force microscopy

Application of atomic force microscopy (AFM) to biological objects and processes under physiological conditions has been hampered so far by the deformation and destruction of the soft biological materials invoked. Here we describe a new mode of operation in which the standard V-shaped silicon nitride cantilever is oscillated under liquid and damped by the interaction between AFM tip and sample surface. Because of the viscoelastic behavior of the cellular surface, cells effectively "harden" under such a tapping motion at high frequencies and become less susceptible to deformation. Images obtained in this way primarily reveal the surface structure of the cell. It is now possible to study physiological processes, such as cell growth, with a minimal level of perturbation and high spatial resolution (approximately 20 nm).     

The benefits of patient education

In this article, the role of the nurse in patient education is described, as well as the benefits of patient education, such as improved quality of care, improved patient satisfaction, increased compliance, improved staff satisfaction, and effective use of resources. Strategies for effective patient teaching also are presented.     

The benefits of back pain

During recent years the gap between the rapid implementation of new technologies in cancer prevention and the slow development of a complementary psychological framework to conceptualize the transmission of genetic informations to patients has been deplored. Such a framework should include all psychological aspects surrounding the genetic consultation, reaching from the information and education of the general public to the impact of prophylactic surgery. While some of the psychological consequences of modern cancer prevention can not be fully foreseen and have first to be documented and analysed, others can easily be anticipated. The authors will try to outline a psychological framework that could help in facing potential negative effects of these beneficial preventive possibilities.     

高分辨连续光源原子吸收光谱法测定铀铌铅多金属矿中痕量银

铀铌铅多金属矿组成成分复杂,准确有效的测定其中的痕量银,有利于银的回收利用。采用HCl-HNO₃-HF-HClO₄处理铀铌铅多金属矿样品,以HCl(1+4)-2g/L酒石酸为测定介质,以λ_Ag=328.068nm为分析谱线,建立了高分辨连续光源原子吸收光谱法(HR-CS-AAS)测定铀铌铅多金属矿样品中痕量银的新方法。对仪器参数进行了优化,确定采用迭代基线校正(IBC)背景校正方式,CCD检测器有效像素点选择5个;由银的平均吸收光谱图和吸光度-波长-时间三维吸收光谱图可知,银的CCD检测器分辨率为0.0020nm/pixel,λ_Ag=328.068nm在327.86~328.27nm范围内没有受到溶液中其他共存元素的谱线干扰。在优化的实验条件下,银的吸光度与其质量浓度在0.40~1.60μg/mL范围内运用二次方程最小二乘法拟合校准曲线,相关系数为0.9999,特征浓度为0.0148μg/mL,方法检出限为0.0013μg/mL。将HR-CS-AAS测定样品中银的参数与空心阴极灯原子吸收光谱法(HCL-AAS)相比,其检出限更低,特征浓度更低,标准溶液系列的吸光度更高。按照实验方法对铀铌铅多金属矿样品中的银进行测定,结果与电感耦合等离子体质谱法基本一致,相对标准偏差(RSD,n=9)为0.63%~3.3%。按实验方法在铀铌铅多金属矿样品中加入银标准溶液进行加标回收试验,回收率为97%~104%,满足国家地质矿产行业标准DZ/T 0130—2006的要求。     

高分辨连续光源原子吸收光谱法测定煤中硫

提出一种用HNO3、HClO4和HF消解样品、高分辨连续光源原子吸收光谱法测定硫在富燃空气-乙炔火焰中形成的CS双原子分子的吸收来测定煤中硫的新方法。实验用含硫标准溶液和煤的标准物质优化了仪器条件,并用不同混合酸对煤样的消解方法进行了比较。对可能存在的光谱和化学干扰、有机溶剂对硫的化合物CS吸收的影响进行了研究。结果表明：除了Fe 258.045 nm线与CS　258.056 nm线的波长差小于0.015 nm外,其他元素干扰线与CS线的波长差均大于0.015 nm,因此可以通过仪器的高分辨率使这些干扰线与CS线分开,克服干扰;Fe　258.045谱线虽然不能与CS　258.056 nm谱线完全分离,但是该谱线在富燃乙炔空气火焰中的吸收强度很弱,不能形成真正的干扰;Pb与溶液中的SO42-反应产生PbSO4沉淀降低了CS的吸收,可在溶液中加入乙酸铵溶液,使SO42-从PbSO4沉淀中释放出来而消除铅的干扰;HNO3、HClO4对CS的吸收影响不明显;在研究的甲醇、乙醇、乙酸、乙腈和丙酮5种有机溶剂中,只有乙醇对CS吸收有较显著的抑制作用,丙酮和乙腈能显著提高CS的吸收。对于CS　3条吸收线（257.594,258.056,257.961 nm）,硫校准曲线的线性范围均为50～1 000 mg/L,检出限分别为34 mg/L,21 mg/L,12 mg/L。本方法用于煤标准物质和煤层样品中硫的测定,测定值与认定值相符,测定结果的相对标准偏差在0.053%～0.082%间（n=5）。     

Limited proteolysis of a trypanosomal hypoxanthine phosphoribosyltransferase yields crystals that diffract X-rays to near atomic resolution

BACKGROUND: Adrenomedullin is a newly identified peptide with profound hypotensive effects. We investigated perioperative adrenomedullin levels among patients with congenital heart disease with and without pulmonary hypertension. METHODS: Levels of plasma adrenomedullin, endothelin-1, and nitric oxide metabolites were measured in three groups: (1) low pulmonary flow (n=11); (2) high flow/low pulmonary arterial pressure (less than 60% systemic pressure) (n=9); and (3) high flow/high pressure (n=10). Samples were obtained preoperatively, on and off pump, and 3, 6, and 12 hours after bypass. RESULTS: Adrenomedullin levels were highest in the low pulmonary flow group (189.7+/-15 pg/mL low flow versus 103.1+/-9.5 pg/mL high flow/low pulmonary and 139+/-17.5 pg/mL high flow/high pressure at 12 hours; p < or = 0.05). The arterial pressure/systemic pressure remained significantly lower in the high flow/low pulmonary pressure compared with the high flow/high pressure group (0.37+/-0.08 versus 0.62+/-0.11; p < 0.005). Perioperative endothelin-1 and nitric oxide levels remained low in the low pulmonary flow group but increased progressively in both high flow groups. CONCLUSIONS: Circulating plasma adrenomedullin appears to affect baseline vascular tone in patients with intact endothelial function. It may interact with nitric oxide and endothelin-1 to help regulate blood pressure perioperatively in patients with congenital heart disease.     

The invisible benefits of exercise.

Objective: To examine whether—and why—people underestimate how much they enjoy exercise. Design: Across four studies, 279 adults predicted how much they would enjoy exercising, or reported their actual feelings after exercising. Main Outcome Measures: Main outcome measures were predicted and actual enjoyment ratings of exercise routines, as well as intention to exercise. Results: Participants significantly underestimated how much they would enjoy exercising; this affective forecasting bias emerged consistently for group and individual exercise, and moderate and challenging workouts spanning a wide range of forms, from yoga and Pilates to aerobic exercise and weight training (Studies 1 and 2). We argue that this bias stems largely from forecasting myopia, whereby people place disproportionate weight on the beginning of a workout, which is typically unpleasant. We demonstrate that forecasting myopia can be harnessed (Study 3) or overcome (Study 4), thereby increasing expected enjoyment of exercise. Finally, Study 4 provides evidence for a mediational model, in which improving people's expected enjoyment of exercise leads to increased intention to exercise. Conclusion: People underestimate how much they enjoy exercise because of a myopic focus on the unpleasant beginning of exercise, but this tendency can be harnessed or overcome, potentially increasing intention to exercise. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The resolution of conflict.

Describes a series of studies investigating the influence of predisposition, structure, and experience on interpersonal conflict. These factors are all inextricably and nonrecursively related. Structure and predisposition influence motive and perceived motive. Experiencing cooperation in a dynamic process conflict situation had little influence on trust or competition, and the experience of noncooperation was far more persistent than the experience of cooperation. The validity of experimental conflict research is explored, and conflict resolution in practice is discussed, focusing on Canada's role in the quest for world peace. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

高分辨连续光源石墨炉原子吸收光谱法测定低铁石英砂中铁

低铁石英资源创新应用技术的发展需要对影响其品质的关键性铁元素含量进行准确的测定。采用15 mL氢氟酸和2 mL硝酸预先于150 ℃浸泡2 h,再加入2 mL高氯酸于180 ℃进行敞开酸消解,最后用1 mL硝酸和1 mL水进行提取。选择248.327 nm波长,采用高分辨连续光源石墨炉原子吸收光谱仪对样品溶液中铁含量进行测定,建立了低铁石英砂中痕量杂质铁的测定方法。对溶样方法、石墨炉升温程序、原子化读数时间、有效像素点等进行了条件优化。结果表明,在20~100 ng/mL的铁质量浓度范围内,以最小二乘法拟合吸光度与质量浓度的校准曲线方程,决定系数达0.999 8,方法检出限为0.002 49 μg/g,定量限为0.007 47 μg/g。采用实验方法测定8个低铁石英砂样品中的杂质铁含量,结果与电感耦合等离子体质谱法基本一致,5次平行测定的相对标准偏差(RSD)介于2.2%至4.8%之间,加入铁标准溶液进行加标回收试验的回收率在90%~110%之间,满足国家地质矿产行业标准DZ/T 0130—2006对回收率的要求。