眼内灌注液中氯化钙含量测定方法改良

目的对眼内灌注液中氯化钙含量测定终点判断方法的改良。方法按文献[1]方法加入试剂和被测物,然后加热再按规定测定氯化钙含量。结果测定终点突跃明显,终点容易判断,误差较小。结论本方法准确可靠。     

电位滴定法测定酮康唑含量能力验证的结果分析

以酮康唑为模型药物,统计了CNAS T0382电位滴定法测定药品含量能力验证的结果,并对离群数据进行技术分析.     

Automatic CPAP Performance in Patients with Sleep Apnea Plus COPD

Abstract

Background: Automatic CPAP devices have demonstrated good results in obtaining optimal fixed CPAP pressure to eliminate respiratory events in patients with sleep apnea-hypopnea syndrome (SAHS). However, automatic CPAP has not been fully studied in patients with COPD plus SAHS. Objectives: To analyse the performance of an automatic CPAP in severe COPD patients compared with SAHS patients with no associated co-morbidity. Methods: We compared 10 consecutive patients with SAHS and no associated co-morbidity and 10 patients with SAHS plus severe COPD who required CPAP titration. Automatic CPAP performance was studied during full-night PSG. Inadequate pressure increase periods, absence of pressure increases in reaction to respiratory events, air leak periods, and pressure behaviour in the face of erratic breathing periods were analysed. Results: The SAHS patients without co-morbidities vs. SAHS plus COPD patients presented: mean sleep efficiency, 80.2 (11.5)% vs. 76.5 (12.1)%; residual AHI, 6.3 (5.2) vs. 5.1 (7.7); residual CT90, 1 (3)% vs. 14 (1)%. The device´s performance demonstrates a mean of 1.2 (1.5) vs. 1.3 (1.2) periods of inadequate pressure increases; absence of pressure increases in reaction to respiratory events, 4.1 (5.4) vs. 0.6 (0.7) times; periods of air leaks, 1.3 (3.8) vs. 13.9 (11.7); mean optimal pressure, 9.1 (1.4) vs. 9.0 (1.9) cm H₂O. Conclusion: Titration with automatic CPAP could be as effective in patients with SAHS plus severe COPD as in patients with SAHS without COPD. However, the presence of more leakages must be taken into account.     

用自动电位滴定仪测定水中氯化物

目的 探讨用自动电位滴定仪测定水中的氯化物含量，为低含量氯化物的测定提供了新的方法依据。方法 用DL53自动电位滴定仪和141－SC银电极各种水样的氯化物含量。结果 采用自动电位滴定仪12份水样中氯化物与国标方法中的人工滴定法所测是的结果作比较，差异无显著性（P＞0．05）。对不同浓度范围氯化物标准溶液进行滴定，其回收率为98．0％－103．7％，相对标准偏差为0．16％。结论 民位滴定法具有容易掌握，测定快速，准确等优点，是值得广泛应用的分析方法。     

脱毛霜(膏)类样品氢氧化物测定的电位滴定法

目的建立脱毛霜(膏)类样品中氢氧化物的测定方法,为国家制订脱毛霜(膏)类样品中氢氧化物的检测方法提供依据.方法采用电位滴定法.结果方法的相对标准偏差均＜1.61%,具有良好的精密度.结论方法使用的仪器普及面广.     

Ge－132含量的中和测定

探讨了中和法测定Ｇｅ－１３２含量的可行性，并与分光光度法对照，结果表明二者有很好的相关性（ｒ＝０．９９５７），样品测定结果基本一致。     

甲磺酸培氟沙星的示波极谱滴定法研究

对甲磺酸培氟沙星含量的示波极谱滴定法测定进行了研究。在 pH5 2的HCl NaAc缓冲溶液中 ,四苯硼钠 (Na TPB)与甲磺酸培氟沙星作用可生成 1∶1定量沉淀 ,过滤弃去初滤液 ,用硫酸亚铊标准溶液滴定续滤液中过量的Na TPB ,通过示波极谱图 (dE/dt=f(E)曲线 )上TPB的切口消失指示滴定终点。本法操作简单、快速 ,终点直观 ,应用于多批原料药样品的测定 ,获得了满意的结果 ,其回收率为 99 4 6 %～ 1 0 0 4 % ,相对误差 <± 0 .6 % ,与部颁标准非水滴定法测得的结果基本一致。     

含硫药物的氧瓶燃烧—电位滴定法测定

建立了一种测定含硫药物的方法。利用氧瓶燃烧法使分子中的硫元素转化为ＳＯ４２－，然后通过蒸发，加维生素Ｃ分解过氧化氢以及加入无水乙醇和１．４—二氧六环等步骤，再用硝酸铅标准溶液以铅离子选择性电极作指示电极进行电位滴定，籍此测定含硫药物的含量。用此法测定了一组含硫药物原料药和几种制剂，经与药典法比较，结果一致。方法简便，在混合物分析中有一定的选择性。     

微量板酶免疫斑点法测定麻疹病毒滴度

测定麻疹病毒滴度常用微量板细胞病变法（ＣＰＥ）或蚀斑法。为简化实验结果判定过程，使实验指标判定更客观，我们在ＣＰＥ方法基础上建立了微量板酶免疫斑点法（Ｍｉｃｒｏｐｌａｔｅｅｎｚｙｍｅｉｍｍｕｎｏｓｐｏｔｓ，ＭＥＩＳ）。该方法通过酶促底物显色和抗原———抗体特异反应，使培养板上感染病毒造成细胞病变的部位形成可见的染色斑点。经肉眼直接观察，以培养板孔底出现特异性染色斑点为病变阳性，计算半数细胞感染浓度（ＣＣＩＤ５０），免去了显微镜下观察细胞病变的过程。经测定５０批麻疹病毒，ＭＥＩＳ法与ＣＰＥ法比较，结果ＣＣＩＤ５０符合率为９８．０％（４９／５０）；实验共用８００板孔，各孔结果总符合率为９９．８８％（７９９／８００），敏感性１００％（５１０／５１０），特异性９９．６６％（２８９／２９０）。本实验方法是敏感、特异的滴定麻疹病毒的新方法，尤其适用于多份病毒的滴定。     

Ion-binding properties of a K+ channel selectivity filter in different conformations

K⁺ channels are membrane proteins that selectively conduct K⁺ ions across lipid bilayers. Many voltage-gated K⁺ (K_V) channels contain two gates, one at the bundle crossing on the intracellular side of the membrane and another in the selectivity filter. The gate at the bundle crossing is responsible for channel opening in response to a voltage stimulus, whereas the gate at the selectivity filter is responsible for C-type inactivation. Together, these regions determine when the channel conducts ions. The K⁺ channel from Streptomyces lividians (KcsA) undergoes an inactivation process that is functionally similar to K_V channels, which has led to its use as a practical system to study inactivation. Crystal structures of KcsA channels with an open intracellular gate revealed a selectivity filter in a constricted conformation similar to the structure observed in closed KcsA containing only Na⁺ or low [K⁺]. However, recent work using a semisynthetic channel that is unable to adopt a constricted filter but inactivates like WT channels challenges this idea. In this study, we measured the equilibrium ion-binding properties of channels with conductive, inactivated, and constricted filters using isothermal titration calorimetry (ITC). EPR spectroscopy was used to determine the state of the intracellular gate of the channel, which we found can depend on the presence or absence of a lipid bilayer. Overall, we discovered that K⁺ ion binding to channels with an inactivated or conductive selectivity filter is different from K⁺ ion binding to channels with a constricted filter, suggesting that the structures of these channels are different.K⁺ channels are found in all three domains of life, where they selectively conduct K⁺ ions across cell membranes. Specific stimuli trigger the activation of K⁺ channels, which results in a hinged movement of the inner helix bundle (1–7). This opening on the intracellular side of the membrane initiates ion conduction across the membrane by allowing ions to enter into the channel. After a period, many channels spontaneously inactivate to attenuate the response (8–17). The inactivation process is a timer that terminates the flow of ions in the presence of an activator to help shape the response of the system. Two dominant types of inactivation have been characterized in voltage-dependent channels: N-type and C-type (18). N-type inactivation is fast and involves an N-terminal positively charged “ball” physically plugging the pore of the channel when the membrane is depolarized. C-type inactivation, on the other hand, is a slower process involving a conformational change in the selectivity filter that is initiated by a functional link between the intracellular gate and the selectivity filter (10, 19).Several experimental observations indicate a role for the selectivity filter in C-type inactivation. First, mutations in and around the selectivity filter can alter the kinetics of inactivation (20–23). Second, increasing concentrations of extracellular K⁺ ions decrease the rate of inactivation, as if the ions are stabilizing the conductive conformation of the channel to prevent a conformational change in the selectivity filter (14, 16, 17, 22). Finally, a loss of selectivity of K⁺ over Na⁺ has been observed during the inactivation process in Shaker channels, suggesting a role for the selectivity filter (24, 25). Together, these data indicate that channels in their inactivated and conductive conformations interact with K⁺ ions differently, and suggest that C-type inactivation involves a conformational change in the selectivity filter. Although several structures of K⁺ channels in their conductive state have been solved using X-ray crystallography, there is at present no universally accepted model for the C-type inactivated channel (1, 3–5, 9, 19, 26–28) (Fig. 1B).Open in a separate windowFig. 1.Macroscopic recordings and structural models of KcsA K⁺ channel. (A) Macroscopic currents of WT KcsA obtained by a pH jump from pH 8 to pH 4 reveal channel inactivation. Two models representing the conformation of the channel are shown below. (B) Conductive [Left, Protein Data Bank (PDB) ID code 1K4C] and constricted (Right, PDB ID code 1K4D) conformations of the selectivity filter are shown as sticks, and the ion-binding sites are indicated with green spheres. The thermodynamic properties of the conductive, constricted, and inactivated (Middle) conformations are the subject of this study.Inactivation in the K⁺ channel from Streptomyces lividians (KcsA) has many of the same functional properties of C-type inactivation, which has made it a model to understand its structural features (20). KcsA channels transition from their closed to open gate upon changing the intracellular pH from high to low (Fig. 1A). The rapid flux of ions through the channel is then attenuated by channel inactivation, where most open WT channels are not conducting, suggesting that crystal structures of open KcsA channels would reveal the inactivated channel. In some crystal structures of truncated WT KcsA solved with an open gate, the selectivity filter appears in the constricted conformation, similar to the conformation observed in structures of the KcsA channel determined in the presence of only Na⁺ ions or low concentrations of K⁺ ions (3, 10, 29, 30) (Fig. 1B). Solid-state and solution NMR also indicate that the selectivity filter of the KcsA channel is in the constricted conformation when the cytoplasmic gate is open (31–33).However, a recently published study shows that even when the constricted conformation of KcsA’s selectivity filter is prevented by a nonnatural amino acid substitution, the channel inactivates like WT channels, suggesting the constricted filter does not correspond to the functionally observed inactivation in KcsA (28). In this study, we use isothermal titration calorimetry (ITC) to quantify the ion-binding properties of WT and mutant KcsA K⁺ channels with their selectivity filters in different conformations and EPR spectroscopy to determine the conformation of the channels’ intracellular gates. A comparison of these ion-binding properties leads us to conclude that the conductive and inactivated filters are energetically more similar to each other than the constricted and inactivated filters.