光谱法研究环丙沙星与牛血清白蛋白的相互作用

用荧光光谱法、紫外光谱法研究了生理条件下环丙沙星(CPFX)与牛血清白蛋白(BSA)相互作用的光谱特性。测定了CPFX与BSA在18、28℃两个温度下的结合常数KA(18℃:5.75×105L.mol-1,28℃:1.54×105L.mol-1)和结合位点数n(18℃:0.99,28℃:0.93)。结果表明:CPFX对BSA有明显的猝灭作用,其方式为静态猝灭。由热力学参数分析其结合力主要是氢键和范德华力。同步荧光分析的结果表明CPFX的存在改变了牛血清白蛋白的分子构象。     

铽-环丙沙星与罗丹明B间稀土敏化荧光能量转移机理研究

利用荧光光谱法及紫外光谱法研究发现pH6.2醋酸-醋酸钠(HAc-NaAc)水溶液中铽与环丙沙星形成络合物使铽在490,545,590nm处出现Tb3 的特征发射峰即荧光被强烈的敏化增强,且在545nm处的荧光强度最大,铽离子的锐线发射光谱的特征最强峰545nm与罗丹明B的最大吸收峰波长552nm十分接近,能够发生能量转移反应。因此,随着碱性染料罗丹明B的加入铽-环丙沙星的特征荧光呈现有规律降低,表明罗丹明B对铽-环丙沙星荧光有猝灭作用,研究结果表明其猝灭类型主要为静态猝灭。又根据Frster理论,测得了罗丹明B对铽-环丙沙星的能量转移效率,相互结合距离等参数。从而进一步证明了该反应是单一静态猝灭过程,阐述了其荧光猝灭机理是通过能量转移产生的。     

乳酸亚铁中总铁的溶样及比色测定

本文研究在ＨＮＯ３－ＨＣｌ体系乳酸亚铁中的Ｆｅ＾２＋会被氧化成Ｆｅ＾３＋，用碘基水杨酸比色法就能准确测定总铁量，回收率在９８％－１００％，相对标准偏差为１．１４％，摩尔吸光系数为５．６×１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１，含铁量在０－７００μｇ／１００ｍＬ范围内符合比耳定律。     

环丙沙星的光谱性质、质子化作用与荧光量子产率

研究了环丙沙星(ciprofloxacin, CIP)在不同pH条件下的荧光光谱、紫外吸收光谱和质子化作用,测量了CIP在中性条件下的荧光量子产率。在H+浓度大于1 mol·L-1的HCl介质中,CIP分子(简写为HL)可以结合3个质子而以H₄L3+形式存在,有微弱的荧光,最大荧光发射波长(λ_ｍａｘ)为456 nm。在pH 0～2的酸性条件下,CIP主要以H₃L2+形式存在,λ_ｍａｘ为450 nm,荧光较弱,荧光强度随pH的升高而上升。在pH 2～4时,CIP主要以H₂L+形式存在,具有强荧光,λ_ｍａｘ仍为450 nm。当pH＞4时,λ_ｍａｘ逐步蓝移到414 nm,荧光强度随pH的升高而稍有降低,同时紫外吸收光谱也有明显变化,表明H₂L+随pH升高而失去质子,以双极离子HL形式存在。当pH＞8时,荧光强度随pH升高而减弱至消失,表明HL逐步失去质子,转化为无荧光的阴离子L-。在分子形态变化过程中,最大荧光激发波长始终在275 nm附近,但最大荧光发射波长有较大变化。在pH 7.0的缓冲溶液中,以硫酸奎宁为参比,测得CIP在最大荧光激发波长275 nm处的荧光量子产率为0.12。     

紫外分光光度法测定司帕沙星注射液主含量

紫外分光光度法测定乳酸司帕沙星葡萄糖注射液的含量。司帕沙星浓度在2—12μg／mL范围内与吸光度呈良好的线性关系。回收率为99．8％-100．1％，RSD为0．1％。该法简便、快速，重复性好，结果准确可靠。     

In vivo C magnetic resonance spectroscopy of a human brain tumor after application of C-1-enriched glucose

Objectives

As a unique tool to assess metabolic fluxes noninvasively, ¹³C magnetic resonance spectroscopy (MRS) could help to characterize and understand malignancy in human tumors. However, its low sensitivity has hampered applications in patients. The aim of this study was to demonstrate that with sensitivity-optimized localized ¹³C MRS and intravenous infusion of [1-¹³C]glucose under euglycemia, it is possible to assess the dynamic conversion of glucose into its metabolic products in vivo in human glioma tissue.

Materials and Methods

Measurements were done at 3 T with a broadband single RF channel and a quadrature ¹³C surface coil inserted in a ¹H volume coil. A ¹H/¹³C polarization transfer sequence was applied, modified for localized acquisition, alternatively in two (50 ml) voxels, one encompassing the tumor and the other normal brain tissue.

Results

After about 20 min of [1-¹³C]glucose infusion, a [3-¹³C]lactate signal appeared among several resonances of metabolic products of glucose in MR spectra of the tumor voxel. The resonance of [3-¹³C]lactate was absent in MR spectra from contralateral tissue. In addition, the intensity of [1-¹³C]glucose signals in the tumor area was about 50% higher than that in normal tissue, likely reflecting more glucose in extracellular space due to a defective blood–brain barrier. The signal intensity for metabolites produced in or via the tricarboxylic acid (TCA) cycle was lower in the tumor than in the contralateral area, albeit that the ratios of isotopomer signals were comparable.

Conclusion

With an improved ¹³C MRS approach, the uptake of glucose and its conversion into metabolites such as lactate can be monitored noninvasively in vivo in human brain tumors. This opens the way to assessing metabolic activity in human tumor tissue.     

Polymeric FAD used as enzyme-friendly mediator in lactate detection

We present the fabrication and properties of lactate biosensors. The novel feature is the use of polymerized flavin adenine dinucleotide (FAD) as mediator for electron transfer. The biosensors were prepared using lactate dehydrogenase (LDH), lactate oxidase (LOX), or baker's yeast (BY) immobilized at the surface of the electrode. The sensors using purified enzymes showed good sensitivity, linearity, and stability. The sensitivity of the BY electrodes was slightly lower. The advantages of this type of sensors are discussed in connection with potential applications.     

Stereoselective routes to chiral 2-hydroxy-4-oxo acids and substituted 2-hydroxybutyrolactones using lactate dehydrogenases

The enantioselective reduction 2,4-dioxo acids catalysed by lactate dehydrogenases provided access to 2-hydroxy-4-oxo acids of both S and R configuration. Subsequent diastereoselective chemical reduction affords 4-substituted 2-hydroxybutyrolactones.     

High-throughput measurements of ciprofloxacin,clomipramine and fexofenadine hydrochlorides with an 8-channel electrical titrator

By employing a developed automatic eight-channel electrical titrator, ciprofloxacin, clomipramine and fexofenadine hydrochlorides are determined in batch, respectively, with satisfactory accuracy and precision. It shows a higher efficiency superior to traditional titration method, and maximally 30 measurements per minute can be completed.