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1.
Bromination of dehydroacetic acid has been carried out with N-bromosuccinimide under various conditions. The reactions led to selective bromination, thereby offering efficient synthesis of 3β-bromodehydroacetic acid (3), 3β,5-dibromodehydroacetic acid (4), 3β,3β-dibromodehydroacetic acid (5), and 3β,3β,5-tribromodehydroacetic acid (6). 相似文献
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ABSTRACT The interaction between phenformin hydrochloride and bovine serum albumin (BSA) was investigated by the methods of chemiluminescence combined with equilibrium dialysis technique. A novel N-bromosuccinimide (NBS)–eosin Y (EY) chemiluminescence (CL) method was established for the determination of phenformin. The mechanism of this chemiluminescence system was proposed. Optimization studies were performed to determine the phenformin. Under the optimal conditions, the CL intensity was linear for a phenformin concentration over the range of 4.6 × 10?8 to 5.0 × 10?5 g/mL. The detection limit was 1.5 × 10?8 g/mL. The data obtained by the present equilibrium dialysis–CL system were analyzed using the Klotz plot and the Scatchard analysis. The results showed that the Klotz plot and the Scatchard plot are linear with good correlation coefficient, indicating that the phenformin has only one type of binding site on BSA. The binding parameters were the number of the binding sites n (1.02) and the estimated association constant K (2.66 × 104 L/mol). The chemiluminescence system combined with equilibrium dialysis developed in this work demonstrated its use for determination of interaction between drug and protein by using relatively simple instrument. 相似文献
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Sneha Sudha Komath Musti J. Swamy 《Journal of photochemistry and photobiology. B, Biology》1999,50(2-3):108-118
Fluorescence quenching and time-resolved fluorescence studies have been performed on the galactose-specific lectin purified from snake gourd (Trichosanthes anguina) seeds, in order to investigate the tryptophan accessibility and environment in the native protein and in the presence of bound ligand. Estimation of the tryptophan content by N-bromosuccinimide modification in the presence of 8 M urea yields four residues per dimeric molecule. The emission spectrum of native lectin in the absence as well as in the presence of 50 mM methyl--d-galatopyranoside (MeGal) shows a maximum around 331 nm, which shifts to 361.8 nm upon reduction of the disulfide bonds and denaturation with 8 M urea, indicating that all four tryptophan residues in the native state of this protein are in a hydrophobic environment. The extent of quenching that is observed is highest with acrylamide, intermediate with succinimide, and low with Cs+ and I−, further supporting the idea that the tryptophan residues are predominantly buried in the hydrophobic core of the protein. The presence of MeGal (50 mM) affects the quenching only marginally. Time-resolved fluorescence measurements yield bi-exponential decay curves with lifetimes of 1.45 and 4.99 ns in the absence of sugar, and 1.36 and 4.8 ns in its presence. These results suggest that the tryptophan residues are not directly involved in the saccharide binding activity of the T. anguina lectin. Of the four quenchers employed in this study, the cationic quencher, Cs+, is found to be a very sensitive probe for the tryptophan environment of this lectin and may be useful in investigating the environment of partially buried tryptophan residues and unfolding processes in other proteins as well. 相似文献
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N-溴代丁二酰亚胺与天然橡胶(NR)反应合成了大分子引发剂——溴代天然橡胶[NR-Br(1)].通过原子转移自由基聚合(ATRP),以CuBr/PMDTA为催化体系,1引发甲基丙烯酸甲酯(MMA)接枝共聚制得新型天然橡胶-g-聚甲基丙烯酸甲酯[NR-g-PMMA(2)],其结构经1H NMR和IR表征.初步聚合反应动力学研究结果表明,NBS与NR在高温下反应容易伴随双键加成和环化反应,于室温反应所得1具有较高的引发活性;接枝聚合符合一级动力学反应,即2的分子量随MMA单体转化率的提高而增加. 相似文献
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以水为反应介质、NBS为氧化剂,在水相无催化剂条件下实现了醇的氧化.芳香醇、脂肪醇都可以达到95%以上的醛(或酮)产率,但该体系对一些含供电子取代基的醇的反应活性不高,选用salen-Co(Ⅲ)配合物作为催化剂,可拓宽反应的底物适用范围. 相似文献
6.
《Journal of Coordination Chemistry》2012,65(8):1324-1338
[CrIII(LD)(Urd)(H2O)4](NO3)2?·?3H2O (LD?=?Levodopa; Urd?=?uridine) was prepared and characterized. The product of the oxidation reaction was examined using HPLC. Kinetics of the oxidation of [CrIII(LD)(Urd)(H2O)4]2+ with N-bromosuccinimide (NBS) in an aqueous solution was studied spectrophotometrically, with 1.0–5.0?×?10?4?mol?dm?3 complex, 0.5–5.0?×?10?2?mol?dm?3 NBS, 0.2–0.3?mol?dm?3 ionic strength (I), and 30–50°C. The reaction is first order with respect to [CrIII] and [NBS], decreases as pH increases in the range 5.46–6.54 and increases with the addition of sodium dodecyl sulfate (SDS, 0.0–1.0?×?10?3?mol?dm?3). Activation parameters including enthalpy, ΔH*, and entropy, ΔS*, were calculated. The experimental rate law is consistent with a mechanism in which the protonated species is more reactive than its conjugate base. It is assumed that the two-step one-electron transfer takes place via an inner-sphere mechanism. A mechanism for this reaction is proposed and supported by an excellent isokinetic relationship between ΔH* and ΔS* for some CrIII complexes. Formation of [CrIII(LD)(Urd)(H2O)4]2+ in vivo probably occurs with patients who administer the anti-Parkinson drug (Levodopa), since CrIII is a natural food element. This work provides an opportunity to identify the nature of such interactions in vivo similar to that in vitro. 相似文献
7.
铁矿石经盐酸溶解后,用H2O2氧化,使Fe^2+氧化成Fe^3+。加入过量的VC还原Fe^3+,剩余VC用NBSM滴定。方便简便,快速,终点敏锐,精了,准确度高,RSD≤0.3%,相对误差〈0.4%,并可选择性地滴定矿石中的三价铁。 相似文献
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A thymine and acridine conjugate (1), containing a benzylic carbon of thymine and an electron-rich aromatic ring (acridine) within the same molecule, was synthesized. Treatment of 1 with N-bromosuccinimide (NBS) in anhydrous chloroform in the presence of azobisisobutylnitrile produced a dibromo-substituted thymine–acridine conjugate (7) as a major product, in which the bromination was only observed on the acridine ring. Nuclear Overhauser effect (NOE) difference spectroscopy revealed that the actual bromination substitution was on C-2 and C-7 of acridine. Our results suggest that electrophilic aromatic substitution, not the expected benzylic radical reaction, takes place predominantly even when 1 is subjected to the NBS reaction condition, which favors radical processes. In addition, such selectivity is clearly solvent dependent. 相似文献