Heteroassociation of antibiotic norfloxacin with aromatic vitamins in aqueous solution

The heteroassociation of the antibacterial antibiotic norfloxacin with aromatic vitamins nicotineamide and flavin mononucleotide in aqueous solution has been studied by 1H NMR spectroscopy (503 MHz). Equilibrium constants, induced proton chemical shifts, and the thermodynamic parameters (deltaH, deltaS) of the heteroassociation of molecules were determined from the concentration and temperature dependences of chemical shifts of protons of interacting aromatic molecules. An analysis of the results indicates the formation of heterocomplexes between the molecules of the vitamins and norfloxacin, which is caused by stacking interactions between aromatic chromophores and an additional intermolecular hydrogen bond in the norfloxacin-nicotinamide system. Based on the analysis of induced chemical shifts of protons of molecules, the most probable spatial structures 1:1 of norfloxacin-flavin mononucleitide and norfloxacin-nicotinamide heterocomolexes were determined by the methods of molecular modeling using the X-PLOR program.     

Complexation of the quinolone antibiotic norfloxacin with DNA

¹H-NMR spectroscopy (500 MHz) was used to study the complexation of the antibacterial agent norfloxacin (NOR) with DNA tetramers 5′-d(TpGpCpA) and 5′-d(CpGpCpG) in aqueous solution. For the first time, the equilibrium parameters (equilibrium constants, enthalpy, and entropy) were obtained for NOR binding with single-stranded and duplex DNA tetramers. By analyzing the complexation parameters and the induced proton chemical shifts in NOR in various complexes, the character of NOR binding was identified as intercalation in the case of the duplex tetramers and as intercalation with external binding in the case of single-stranded tetramers. NOR proved to preferentially bind to GC sites in DNA duplexes.     

Heteroassociation of Caffeine with the Antibiotic Actinocyl- bis(3-dimethylaminopropylamine) in Aqueous Solution: 1H NMR Analysis

The heteroassociation of caffeine (CAF) and the synthetic antibiotic actinocyl-bis(3-dimethylaminopropylamine) (ACT) was studied in aqueous solution by one- and two-dimensional ¹H NMR spectroscopy at 500 MHz. The equilibrium reaction constants, thermodynamic parameters (H and S) of ACT heteroassociation with CAF, the limiting values of proton chemical shifts of their molecules in the heteroassociation complex, and the spatial structure of the ACT–CAF complex were determined from the experimental dependences of proton chemical shifts of the aromatic molecules on concentration and temperature. The parameters of CAF heteroassociation with the phenoxazone antibiotic actinomycin D and its synthetic analogue ACT were comparatively analyzed and conclusions were made on the crucial role of stacking interactions of the chromophores of CAF and the phenoxazone antibiotics in the formation of the heterocomplexes in aqueous solution.     

Interaction between aromatic antibiotics and vitamins: 1H NMR study of heteroassociation of nicotinamide and anthracycline antitumor antibiotics

The interaction of the anthracycline antitumor antibotics daunomycin and novatrone with the vitamin nicotinamide has been studied by one-and two-dimensional ¹H NMR (500 MHz). Due to significant differences between the structures of the chromophores of interacting molecules, a two-site heteroassociation model has been developed, which implies the binding of one or several nicotinamide molecules to the chromophore of the antibiotic. The structural and thermodynamic parameters of the heteroassociation of nicotinamide with daunomycin and novatrone have been determined from the experimental concentration and temperature dependences of the ¹H NMR chemical shifts of the interacting molecules. The most favorable structures of the 1:1 nicotinamide-daunomycin and nicotinamide-novatrone heterocomplexes have been found using the molecular mechanics method (X-PLOR software) and analysis of induced proton chemical shifts. The results demonstrate that two nicotinamide molecules cannot simultaneously bind on one side of the chromophore of the daunomycin or novatrone. The 1:1 heterocomplexes of the vitamin with the antibiotics are mainly stabilized by the stacking of aromatic chromophores.     

A Structural and Thermodynamic Analysis of Novatrone and Flavin Mononucleotide Heteroassociation in Aqueous Solution by <Superscript>1</Superscript>H NMR Spectroscopy

A heteroassociation of the antitumor antibiotic novatrone (NOV) and flavin mononucleotide (FMN) in aqueous solution was studied by one- and two-dimentional ¹H NMR spectroscopy (500 MHz) to elucidate the molecular mechanism of the possible combined action of the antibiotic and the vitamin. The equilibrium reaction constants, the induced proton chemical shifts, and the thermodynamic parameters (ΔH and Δ_S) of the NOV and FMN heteroassociation were determined from the concentration and temperature dependences of proton chemical shifts of the aromatic molecules. The most favorable structure of the 1 : 1 NOV-FMN complex was determined by both the method of molecular mechanics (X-PLOR software) and the induced proton chemical shifts of the molecules. An analysis of the results suggests that the NOV-FMN intermolecular complexes are mainly stabilized by stacking interactions of their aromatic chromophores. An additional stabilization is possible due to intermolecular hydrogen bonds. It was concluded that the aromatic molecules of vitamins, in particular, FMN, can form energetically favorable heterocomplexes with aromatic antitumor antibiotics in aqueous solutions, which could result in a modulation of their medical and biological action.     

代谢工程在维生素生产中的应用及研究进展

维生素是维持人体生命活动必需的一类有机物质,机体本身一般不能合成或合成量不足,因此需经食物或其他强化产品获取。目前,维生素产品已广泛应用于医药、食品添加剂、饲料添加剂、化妆品等领域,而且全球对维生素的需求也是呈逐年增长态势。维生素的生产方法主要包括化学合成法和生物合成法。化学合成法通常安全隐患大、反应条件严苛、废物污染严重,相比之下,代谢工程生产维生素绿色环保安全、能耗低,因此建立微生物细胞工厂具有重大的科学意义和应用需求。文中回顾了近30年来代谢工程在维生素生产领域的研究进展,详细阐述了水溶性维生素(维生素B1、B2、B3、B5、B6、B7、B9、B12和维生素C的前体)和脂溶性维生素(维生素A、维生素D的前体、维生素E和维生素K)的生物合成研究现状,并对其发酵生产的瓶颈进行了探讨,最后对合成生物技术创建维生素生产菌种进行了展望。     

Benefiting others and self: Production of vitamins in plants

Vitamins maintain growth and development in humans, animals, and plants. Because plants serve as essential producers of vitamins, increasing the vitamin contents in plants has become a goal of crop breeding worldwide. Here, we begin with a summary of the functions of vitamins. We then review the achievements to date in elucidating the molecular mechanisms underlying how vitamins are synthesized, transported, and regulated in plants. We also stress the exploration of variation in vitamins by the use of forward genetic approaches, such as quantitative trait locus mapping and genome-wide association studies. Overall, we conclude that exploring the diversity of vitamins could provide new insights into plant metabolism and crop breeding.     

Determination of norfloxacin using a terbium-sensitized electrogenerated chemiluminescence method.

A simple electrogenerated chemiluminescence (ECL) analysis method for the determination of norfloxacin (NFLX) is reported. It is based on ECL produced by Na(2)SO(3), which is sensitized by the Tb-NFLX complex. The relative ECL intensity of the Tb(3+)-NFLX-Na(2)SO(3) system is proportional to the amount of NFLX. The optimized experimental conditions were investigated. The linear range and detection limit for NFLX were 1.0 x 10(-10)-8.0 x 10(-7) mol/L and 2.8 x 10(-11) mol/L, respectively. This method was successfully applied to the determination of NFLX in a capsule. NFLX in urine can be directly detected without pretreatment or separation.     

1H-NMR analysis of heteroassociation of caffeine with antibiotic actinomycin D in the aqueous solution

The molecular basis of the action of caffeine as a complex forming agent, an interceptor of aromatic drugs intercalating into DNA was studied by the example of the an anticancer antibiotic actinomycin D examined. The hetero-association of caffeine and actionomycin D was studied by one- and two-dimensional 1H-NMR spectroscopy (500 MHz). Concentration and temperature dependences of the proton chemical shifts of molecules in aqueous solution were measured. The equilibrium reaction constant of hetero-association of caffeine with actinomycin D (K = 246 +/- 48 M-1), the limiting chemical shifts of caffeine protons in complexes were determined. The most favourable structure of the 1:1 caffeine-actinomycin D hetero-complex in aqueous solution was constructed using the calculated values of the induced proton chemical shifts of molecules and the quantum-mechanical iso-shielding curves for caffeine and actinomycin D. The thermo-dynamical parameters of the hetero-complex formation between caffeine and actinomycin D were also determined. The structural and thermo-dynamical analysis showed that dispersive forces and hydrophobic interactions play the major role in hetero-association of caffeine and actinomycin D in aqueous-salt solution. The relative content of different complexes in mixed solutions containing caffeine and actinomycin D was calculated and distinctive features of the dynamic equilibrium of caffeine-actinomycin D hetero-associates were revealed as a function of concentration and temperature. It is concluded that hetero-association of caffeine and actinomycin D molecules a lowers the effective concentration of the drug in solution and hence the pharmacological activity of actinomycin D.     

Effects of imidazolium room temperature ionic liquids on the fluorescent properties of norfloxacin

The effects of 12 imidazolium room temperature ionic liquids (RTILs), including [C_nmim]BF₄, [C_nmim]PF₆, and [C_nmim]Br (n = 4, 6, 8, 10), on the fluorescent properties of norfloxacin were examined. The fluorescence intensity of norfloxacin at 0.1 mg/L in methanol significantly increased with the addition of [C_nmim]BF₄ and [C_nmim]PF₆ into the solvent at 0.1–15.0%. The sensitizing effect may result from the higher viscosity of the RTILs–methanol mixture solvent than that of the methanol itself. However, the quenching effect on fluorescence of norfloxacin was observed in [C_nmim]Br–methanol solvent. The fluorescence intensities of norfloxacin decreased with an increase in the alkyl chain length of the alkyl substituents of the imidazolium ring of RTILs. The main interaction between the RTILs and norfloxacin is not by hydrogen bonding. The fact, that some RTILs can significantly sensitize fluorescence of norfloxacin, indicates that RTILs could be a group of promising solvents for development of sensitive spectrofluorimetric methods for determination of norfloxacin at ultra‐trace levels in environmental samples. Copyright © 2011 John Wiley & Sons, Ltd.     

Interaction of the antibiotic norfloxacin with ionic micelles: pH-dependent binding

The interaction of the antimicrobial drug norfloxacin (NFX) with anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium bromide (CTAB) micelles was studied using the intrinsic spectroscopic properties of NFX to obtain association constants and molecular modifications. Nonionic Tween^® 20 micelles were also investigated, but the spectroscopic properties of NFX did not detect interactions with these micelles, and quenching by iodide suggested a weak association constant around 47 M^?1. For SDS and CTAB, UV–Vis absorption spectroscopy, steady-state and time-resolved fluorometry were monitored as a function of surfactant concentration ranging from the premicellar to micellar region. It was found that cationic (pH 4.0) and zwitterionic NFX (pH 7.4) associate with SDS micelles, with binding constants equal to 5.4 × 10³ and 1.7 × 10³ M^?1, respectively. Premicellar interaction slightly decreases the critical micelle concentration of SDS. Association of anionic NFX (pH 10.6) is very weak. The fluorescence spectrum and lifetime showed that SDS-associated NFX is cationic and that the heterocycle penetrates the interfacial environment of decreased polarity. Cationic CTAB micelles do not bind cationic NFX, and the association constant with zwitterionic NFX is two orders of magnitude lower than that of SDS micelles. From a pharmacological point of view, it is important that at neutral pH, NFX presented a two orders of magnitude higher affinity for anionic than for cationic sites, and did not interact significantly with nonionic or zwitterionic micelle interfaces.     

免疫球蛋白联合B族维生素对癫痫症状及生活质量的影响

目的:探讨免疫球蛋白联合B族维生素对癫痫症状及生活质量的影响.方法:2017年2月至2020年1月选择在本院诊治的癫痫患者78例,根据随机数字表法把患者分为观察组与对照组各39例.两组都给予常规治疗,对照组给予维生素B12治疗,观察组给予免疫球蛋白联合维生素B12治疗,记录两组治疗后症状与生活质量情况.结果:治疗后观察...     

Organelle specific enzyme markers as indicators of methylmercury neurotoxicity and antidotal efficacy in mice

The efficacy of two monothiols, N-acetyl-DL-homocysteine thiolactone (NAHT) and glutathione (GSH) either alone or in combination with two vitamins, vitamin B complex and vitamin E were studied in 7 days methylmercury chloride (MMC; 1 mg kg) intoxicated male Swiss albino mice. Thirteen groups of animals, each containing 6 animals were used for the study. Three groups of animals were kept as control (treated either with vehicle, normal saline or olive oil). Rest of the ten groups were kept as treatment groups. All the animals were treated subcutaneously for 7 days with MMC and one group was sacrificed on the 8th day. The second group was kept without toxicant for another 7 days and were sacrificed on the 15th day. Two MMC pretoxicated groups were treated either with vitamin B complex (20 mg kg) or vitamin E (60 mg kg) and two other groups were treated with N-acetyl-DL-homocysteine thiolactone (40 mg kg) or glutathione (50 mg kg) for another 7 days. The rest of the four groups were treated with either N-acetyl-DL-homocysteine thiolactone or glutathione in combination with either vitamin B complex or vitamin E. All the animals were sacrificed on the 15th day, brain and spinal cord were dissected and estimated for acid phosphatase, alkaline phosphatase, succinic dehydrogenase and mannosidases. Some of the antidotes showed significant recovery of the enzymes in one tissue while some showed significant recovery in the other tissue depicting the need for treating methylmercury poisoned animals with multi-chelation therapy rather than as a monotherapy.     

1H NMR analysis of the complex formation of aromatic molecules of antibiotic and vitamin in aqueous solution: heteroassociation of actinomycin D and flavin mononucleotide

The molecular mechanism of the combined action of antibiotic and vitamin was studied by NMR spectroscopy. The heteroassociation of the antitumor antibiotic actinomycin D and flavin mononucleotide was investigated as a function of concentration and temperature by 500 MHz 1H NMR spectroscopy. The equilibrium association constant, the thermodynamic parameters (deltaH, deltaS) of heteroassociation of actinomycin D with flavin mononucleotide, and the limiting values of proton chemical shifts in the heterocomplex were determined from the concentration and temperature dependences of proton chemical shifts of molecules. The most favorable structure of the 1:1 actinomycin D-flavin mononucleotide heteroassociation complex was determined using both the molecular mechanics methods (X-PLOR software) and the limiting values of proton chemical shifts of the molecules. In the calculated structure, the planes of the chromophores of actinomycin D and flavin mononucleotide molecules in the 1:1 heterocomplex are parallel and separated from each other by a distance of about 0.34 nm. At the same time, there is a probability of formation of intermolecular hydrogen bonds in the calculated structure of 1:1 actinomycin D-flavin mononucleotide complex. The analysis of the results obtained suggests that aromatic molecules of vitamins, e.g., flavin mononucleotide, can form energetically favorable heterocomplexes with aromatic antitumor antibiotics in aqueous solution, modulating thereby the efficacy of their medical and biological action.     

A fluorimetric assay for real-time monitoring of adenylyl cyclase activity based on terbium norfloxacin

Adenylyl cyclases catalyze the production of the second messenger cyclic AMP from ATP. Until now, there has been no fluorescent adenylyl cyclase assay known that is applicable to high-throughput screening and kinetic determinations that can directly monitor the turnover of the unmodified substrate ATP. In this study, a fluorescence-based assay is described using the Ca(II)- and calmodulin-dependent adenylyl cyclase edema factor (EF) from Bacillus anthracis and Tb(III)-norfloxacin as probe for the enzyme activity. This assay can be used to study enzyme regulators, allows real-time monitoring of adenylyl cyclase activity, and does not substitute ATP by fluorescent derivatives. These derivatives must be judged critically due to their interference on the activity of enzymes. Furthermore, the new assay makes redundant the application of radioactively labeled substrates such as [α-³²P]ATP or fluorescently labeled antibodies such as anti-cyclic AMP. We determined the Michaelis-Menten constant (K_M), the v₀^max value of ATP turnover, and the IC₅₀ values for three inhibitors of EF by this newly developed fluorescent method.     

Simultaneous determination of piroxicam and norfloxacin in biological fluids by high‐performance liquid chromatography with fluorescence detection at zero‐order emission mode

A new highly sensitive high‐performance liquid chromatographic method with fluorescence detection (HPLC–FLD) in zero‐order emission mode was developed for the first time for the simultaneous determination of piroxicam (PRX) and norfloxacin (NRF) in biological fluids. The fluorescence detector wavelengths were set at 278 nm for excitation and zero‐order mode for emission. The zero‐order emission mode produced greater sensitivity for the measurement of both drugs than a fixed emission wavelength (446 nm). The new developed method was validated according to International Conference of Harmonization (ICH) guidelines. Linearity was found to be over concentration ranges 0.001–20 μg/ml and 0.00003–0.035 μg/ml for PRX and NRF, respectively. The limits of detection were 4.87 × 10^?4 and 1.32 × 10^?5 μg/ml for PRX and NRF, and the limits of quantitation were 1.47 × 10^?3 and 4.01 × 10^?5 μg/ml, respectively. The current fluorescence method was found to be more sensitive than most commonly used analytical methods and was successfully applied for simultaneous determination of PRX and NRF in biological fluids (serum and urine) with recoveries ranging from 91.67% to 100.36% for PRX and from 96.00% to 101.43% for NRF.     

1H NMR study of the complexation of the quinolone antibiotic norfloxacin with DNA

Complexation of antibiotic norfloxacin (NOR) with DNA fragments 5'-d(TpGpCpA) and 5'-d(CpGpCpG) has been studied in aqueous solution by 1H NMR spectroscopy (500 MHz). Equilibrium parameters of the complexation with single-stranded and duplex forms of DNA oligomer--equilibrium constants, enthalpy and entropy--have been obtained for the first time. Based on the analysis of the complexation parameters as well as induced chemical shifts of the antibiotic protons within different complexes, it was found that NOR binds with the tetramer duplexes mainly by intercalation. The complexation with the single-stranded form may occur either by intercalation and external binding. The site of preferential binding of the antibiotic with DNA duplex is GC site.     

1H-NMR analysis of the heteroassociation of caffeine with the antibiotic actinocyl-bis(3-dimethylaminopropylamine) in aqueous solution

The heteroassociation of caffeine (CAF) and the synthetic antibiotic actinocyl-bis(3-dimethylaminopropylamine) (ACT) was studied in aqueous solution by one- and two-dimensional 1H NMR spectroscopy at 500 MHz. The equilibrium reaction constants, thermodynamic parameters (delta H and delta S) of ACT heteroassociation with CAF, the limiting values of proton chemical shifts of their molecules in the heteroassociation complex, and the spatial structure of the ACT-CAF complex were determined from the experimental dependences of proton chemical shifts of the aromatic molecules on concentration and temperature. The parameters of CAF heteroassociation with the phenoxazone antibiotic actinomycin D and its synthetic analogue ACT were comparatively analyzed and conclusions were made on the crucial role of stacking interactions of the chromophores of CAF and the phenoxazone antibiotics in the formation of the heterocomplexes in aqueous solution.     

Effects of increased levels of supplemental vitamins during the summer in a commercial artificial insemination boar stud

Heat stress due to increasing extremes in ambient temperature and humidity results in reduced semen quality in boars. This has caused reduced efficiency of the swine industry, requiring more boars to breed the same number of sows. Vitamins such as vitamin C (VC) and E (VE) have been shown to improve semen quality in boars. Recently, vitamin D has been shown to improve semen quality in boars. The purpose of this experiment was to evaluate the effects of increased supplemental vitamins on boar reproduction during the summer season in a commercial boar stud. One hundred and sixty Pig Improvement Company (PIC) terminal line boars (n = 32 per treatment) and 39 maternal, heat-sensitive boars (n = 7 or 8 per treatment) were randomly allocated to treatment and fed a corn and soybean meal-based diet adjusted based on individual boar body condition score. A control (CNT) diet was used that met PIC recommendations for boars. Increased supplementation of specific vitamins was given in the form of a top-dress and consisted of CNT wheat middlings, CNT plus VC (560 mg/day), CNT plus 25-hydroxy vitamin D₃ (VD) (125 µg/day), CNT plus VE (275 mg/day) and CNT plus VC, VD and VE (CDE). The experiment was split into three periods based on maximum daily high temperatures in the barn, where period 1 was weeks 1 to 4, period 2 was weeks 5 to 11 and period 3 was weeks 12 to 14. Semen was collected from boars as needed using the stud’s normal production schedule and was analyzed for sperm quantity and quality characteristics. There were no dietary effects on semen volume, sperm concentration or total sperm production (P ≥ 0.553). Total motility of sperm was not impacted by diet (P = 0.115); although, VC tended (P = 0.064) to have a greater progressive motility than CDE. Percentages of morphologically normal sperm and normal acrosomes were not affected by dietary supplementation (P ≥ 0.157). Period effects were observed for most semen quality parameters, with quality generally becoming reduced over time. The present study demonstrates that increased supplementation of vitamins beyond PIC recommendations was not beneficial for boar reproduction during the summer.