黄芪药渣中阿拉伯木聚糖(AX-Ⅰ-1)的提取纯化、结构分析及体外抗氧化作用

黄芪药渣经分级提取,再通过二乙氨乙基(DEAE)-纤维素52阴离子交换柱层析和Sephacryl S-400HR凝胶柱层析分离纯化,得到4个多糖组分AX-Ⅰ-1~AX-Ⅰ-4.对多糖AX-Ⅰ-1的理化性质和结构进行研究发现,AX-Ⅰ-1含有鼠李糖、阿拉伯糖、木糖、甘露糖、葡萄糖和半乳糖(摩尔比为0.006∶14.113∶8.284∶0.116∶0.468∶1),主链由阿拉伯糖和木糖通过β-(1→2),(1→3)和(1→4)苷键组成,支链由(1→4)βArap,(1→3)βGalp和(1→2)βMan组成,非还原末端由αRhap,βGclp和βGalp组成.对多糖AX-Ⅰ-1~AX-Ⅰ-4的抗氧化研究结果表明,这4个组分对羟基自由基、超氧阴离子自由基和1,1-二苯基-2-三硝基苯肼(DPPH)自由基均有一定的清除作用;当浓度为0.1 mg/m L时,多糖AX-Ⅰ-2~AX-Ⅰ-4对超氧阴离子的清除率是阳性对照维生素C(Vc)的2倍.     

Antioxidant, nitric oxide scavenging and malondialdehyde scavenging activities of essential oils from different chemotypes of Zataria multiflora

The antioxidant, nitric oxide (NO) scavenging and malondialdehyde (MDA) scavenging activities of different Zataria multiflora (ZM) chemotype essential oils (EOs) were investigated. The main components are: ZM1 (carvacrol, p-cymene), ZM2 (carvacrol, p-cymene), ZM3 (carvacrol, p-cymene), ZM4 (linalool), ZM5 (carvacrol, p-cymene, thymol), ZM6 (thymol, carvacrol, p-cymene, γ-terpienene), ZM7 (thymol, p-cymene, γ-terpienene) and ZM8 (carvacrol, linalool, p-cymene, thymol). The antioxidant capacities were estimated to be 863?±?55, 619?±?27, 876?±?32, 38?±?9, 649?±?50, 595?±?40, 696?±?41 and 618?±?9?μg ascorbic acid equivalents per millilitre for ZM1 to ZM8, respectively. The NO scavenging values were estimated to be 54?±?1.2, 50?±?1.4, 63?±?1, 0.60?±?0.1, 53?±?0.7, 53?±?1.5, 38?±?1.1 and 46.5?±?3?μg ascorbic acid equivalents per millilitre for ZM1 to ZM8, respectively. The MDA scavenging values were estimated to be 19?±?1, 9?±?1, 24?±?1, 1.6?±?0.6, 12?±?1, 11.7?±?1, 10?±?1 and 12.5?±?1.3?μg ascorbic acid equivalents per millilitre for ZM1 to ZM8, respectively. Among these EOs, ZM3 with carvacrol and p-cymene had higher antioxidant, NO scavenging and MDA scavenging properties.     

Application of response surface methodology in the optimisation of a growth medium for enhanced natural preservative bacteriocin production by a probiotic bacterium

In this study, a statistics-based experimental design was utilised for the optimisation of a growth medium which possibly enhanced bacteriocin production by Streptococcus phocae PI80. Carbon, nitrogen sources and a bio-surfactant were first screened using a one variable at a time technique and scored for increasing yield production. The selected variables were further statistically optimised using response surface methodology with a central composite design. The high- and low-level limits of the selected variables were determined, and a set of 34 experimental runs were performed. The concentration of each medium ingredient influenced the bacteriocin activity to about 22,500?AU?mL?1. The carbon and nitrogen sources were identified as significant factors in restraining the bacteriocin activity produced by S. phocae PI80. The statistics-based experimental design was found to be very efficient in optimising the media components in a number of experimental runs, with a three-fold increase in bacteriocin activity compared to the un-optimised medium. The optimum medium composition was found to be sodium succinate (10.0?g?L?1), yeast extract (4.0?g?L?1), glucose (9.0?g?L?1), NaCl (10.0?g?L?1), Tween 80 (6.0?g?L?1) and K?HPO? (1.0?g?L?1). This optimised medium is two-fold more cost effective than the commercial Lactobacillus MRS medium.     

In vitro antimycobacterial activity and HPLC-DAD screening of phenolics from Ficus benjamina L. and Ficus luschnathiana (Miq.) Miq. leaves

The total phenolic content (Folin-Ciocalteu) of the leaves of Ficus benjamina and Ficus luschnathiana was evaluated and screened by HPLC-DAD. Ficus luschnathiana crude extract (CE) presented phenolic content higher than that of F. benjamina (149.92?±?3.65 versus 122.63?±?2.79?mg of GAE). Kaempferol (1.63?±?0.16?mg?g(-1) dry weight of CE) and chlorogenic acid (17.77?±?0.57?mg?g(-1) of butanolic fraction) were identified and quantified in F. benjamina, whereas rutin (1.39?±?0.20?mg?g(-1)), caffeic (1.14?±?0.13?mg?g(-1)) and chlorogenic (3.73?±?0.29?mg?g(-1)) acids were quantified in the CE of F. luschnathiana. Additionaly, rutin (15.55?±?1.92?mg?g(-1)) and quercetin (3.53?±?0.12?mg?g(-1)) were quantified in ethyl acetate and butanolic fractions, respectively. Antimycobacterial activity of CEs and fractions was evaluated against Mycobacterium smegmatis by broth microdilution method. Ethyl acetate fraction from F. benjamina and n-butanol fraction from F. luschnathiana displayed the highest inhibitory activity (MIC?=?312.50?μg?mL(-1) and 156.25?μg?mL(-1), respectively). Further studies are required to identify the compounds directly related to antimycobacterial activity.     

Two New Steroidal Saponins from Diuranthera inarticulata

There are only three species in the genus Diuranthera (Liliaceae), which is endemic in the southwest of China1. Four steroidal saponins, diuranthosides A-C and chloromalo-side A were isolated from the fresh roots of D. major. This paper deals with the structure elucidation of two new steroidal saponins, diuranthosides D and E, which were isolated from the methanolic extract of whole plant of D. inarticulata Wang et K. Y. Lang.Diuranthoside D (1), [(]-38 (c 0.08, pyridine), afforded galac…     

Potentiometric,spectrophotometric, and AM1d studies of the equilibria between silver(I) ion and monoaza-crown ethers with anthraquinone in various solvents

Complex formation and stability constants between silver(I) and monoaza-12-crown, monoaza-15-crown, and monoaza-18-crown ethers with anthraquinone were determined in acetonitrile, methanol, and propylene carbonate by potentiometric and UV-spectrophotometric methods. Complexes of 1?:?1 and 1?:?2 metal-to-ligand stoichiometry were formed. The solvent composition and the size of the macrocyclic ring affect the stability constants of the complexes. The energetically most favorable structures of the 1?:?1 metal-to-ligand complexes were calculated and visualized by the AM1d method at a semiempirical level of theory.     

Synthesis and Ni(0)-catalyzed oligomerization of isomeric 4,4‴-dichloroquaterphenyls

4,4?-Dichloro-1,1′ : 2′,1″ : 2″,1?-quaterphenyl ( 9 ), 4,4?-dichloro-1,1′ : 3′,1″ : 3″,1?-quaterphenyl ( 10 ), and 4,4?-dichloro-1,1′ : 4′,1″ : 4″,1?-quaterphenyl ( 11 ) were synthesized by Pd (0) catalyzed cross-coupling reaction of 4-chlorobenzeneboronic acid with 2,2′-, 3,3′-, and 4,4′-bis (trifluoromethanesulfonyloxy)biphenyl respectively. 4,4?-Dichloro-1,1′ : 2′,1″ : 2″,1?-quaterphenyl ( 9 ) and 4,4?-dichloro-1,1′ : 3′,1″ : 3″,1?-quaterphenyl ( 10 ) were oligomerized by Ni(0) catalyzed homocoupling reaction to yield white and soluble oligophenylenes. © 1993 John Wiley & Sons, Inc.     

Complexation studies of Cm(III), Am(III), and Eu(III) with linear and cyclic carboxylates and polyaminocarboxylates

Solvent extraction and potentiometric titration methods have been used to measure the stability constants of Cm(III), Am(III), and Eu(III) with both linear and cyclic carboxylates and polyaminocarboxylates in an ionic strength of 0.1?mol?L^?1 (NaClO₄). Luminescence lifetime measurements of Cm(III) and Eu(III) were used to study the change in hydration upon complexation over a range of concentrations and pH values. Aromatic carboxylates, phthalate (1,2 benzene dicarboxylates, PHA), trimesate (1,3,5 benzene tricarboxylates, TSA), pyromellitate (1,2,4,5 tetracarboxylates, PMA), hemimellitate (1,2,3 benzene tricarboxylates, HMA), and trimellitate (1,2,4 benzene tricarboxylates, TMA) form only 1?:?1 complexes, while both 1?:?1 and 1?:?2 complexes were observed with PHA. Their complexation strength follows the order: PHA～TSA>TMA>PMA>HMA. Carboxylate ligands with adjacent carboxylate groups are bidentate and replace two water molecules upon complexation, while TSA displaces 1.5 water molecules of hydration upon complexation. Only 1?:?1 complexes were observed with the macrocyclic dicarboxylates 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N′-diacetate (K21DA) and 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N′-diacetate (K22DA); both 1?:?1 and 1?:?2 complexes were observed with methyleneiminodiacetate (MIDA), hydroxyethyleneiminodiacetate (HIDA), benzene-1,2-bis oxyacetate (BDODA), and ethylenediaminediacetate (EDDA), while three complexes (1?:?1, 1?:?2, and 1?:?3) were observed with pyridine 2,6 dicarboxylates (DPA) and chelidamate (CA). The complexes of M-MIDA are tridentate, while that of M-HIDA is tetradentate in both 1?:?1 and 1?:?2 complexes. The M-BDODA and M-EDDA complexes are tetradentate in the 1?:?1 and bidentate in the 1?:?2 complexes. The complexes of M-K22DA are octadentate with one water molecule of hydration, while that of K21DA is heptadentate with two water molecules of hydration. Simple polyaminocarboxylate 1,2 diaminopropanetetraacetate (PDTA) and ethylenediamine N,N′-diacetic-N,N′-dipropionate (ENDADP) like ethylenediaminetetraacetate (EDTA) form only 1?:?1 complexes and their complexes are hexadentate. Polyaminocarboxylates with additional functional groups in the ligand backbone, e.g., ethylenebis(oxyethylenenitrilo) tetraacetate (EGTA), and 1,6 diaminohexanetetraacetate (HDTA) or with additional number of groups in the carboxylate arms diethylenetriamine pentaacetato-monoamide (DTPA-MA), diethylenetriamine pentaacetato-bis-methoxyethylamide (DTPA-BMEA), and diethylenetriamine pentaacetato-bis glucosaamide (DTPA-BGAM) are octadentate with one water molecule of hydration, except N-methyl MS-325 which is heptadentate with two water molecules of hydration and HDTA which is probably dimeric with three water molecules of hydration. Macrocyclic tetraaminocarboxylate, 1,4,7,10-tetraazacyclododecanetetraacetate (DOTA) forms only 1?:?1 complex which is octadentate with one water molecule of hydration. The functionalization of these carboxylates and polycarboxylates affect the complexation ability toward metal cations. The results, in conjunction with previous results on the Eu(III) complexes, provide insight into the relation between ligand steric requirement and the hydration state of the Cm(III) and Eu(III) complexes in solution. The data are discussed in terms of ionic radii of the metal cations, cavity size, basicity, and ligand steric effects upon complexation.     

CMM-RS potential for characterization of the properties of the halogen-bonded OC-Cl2 complex, and a comparison with hydrogen-bonded OC-HCl

Transitions associated with the vibrations ν?, ν? + ν(b)1, ν? + ν?1, and ν? + ν?1 - ν?1 of the complex OC···Cl? have been rovibrationally analyzed for several isotopologues involving isotopic substitutions in Cl?. Spectra were recorded using a recently constructed near-infrared (4.34 to 4.56 μm), quantum-cascade laser spectrometer with cw supersonic slit jet expansion. Spectral analysis allowed precise determination of the ν?1 intermolecular vibration of OC-3?Cl? to be 25.977637(80) cm?1. These results were incorporated with other previously determined data into a spectroscopic database for generation of a five-dimensional morphed potential energy surface. This compound-model morphed potential with radial shifting (CMM-RS) was then used to make more accurate predictions of properties of the OC-3?Cl? complex including D(e) = 544(5) cm?1, D? = 397(5) cm?1, ν? = 56.43(4) cm?1, and ν(b)1 = 85.43(4) cm?1. The CMM-RS potential determined for OC-Cl? was also used to compare quantitatively many of the inherent properties of this non-covalent halogen bonded complex with those of the closely related hydrogen-bonded complex OC-HCl, which has a similar dissociation energy D?. We found that in the ground state, the CO bending amplitude is larger in OC-Cl? than in OC-HCl.     

Antifungal effect of the essential oil of Thymus broussonetii Boiss endogenous species of Morocco

The aim of the study was to determine the antifungal effects of the essential oil of Thymus broussonetii Boiss (EOT), an endemic plant in Morocco against Candida albicans, Aspergillus fumigatus and the dermatophytes. EOT was extracted by steam distillation. A suspension of up to 500?μL of C. albicans at a concentration of 10??CFU?mL?1 and A. fumigatus at a concentration of 101??spores?mL?1 were inhibited by 20?μL of EOT incorporated in tubes containing 4 mL of Sabouraud broth. In Sabouraud-chloramphenicol agar slants containing different concentrations of essential oil, 5?×?10? A. fumigatus spores were inhibited by 6?μL (0.0015?mL?mL?1) of the EOT. It has shown good anti-C. albicans and anti-A. fumigatus activity. All the dermatophytes tested were inhibited by 3?μL (0.00075?mL?mL?1) of EOT; the latter has the potential to be a good alternative to the conventional antifungal drugs which are usually expensive and with high toxicity.     

Pyrolytic characteristics and kinetics of pistachio shell by thermogravimetric analysis

Pyrolytic characteristics and kinetics of pistachio shell were studied using a thermogravimetric analyzer in 50?C800?°C temperature range under nitrogen atmosphere at 2, 10, and 15?°C?min^?1 heating rates. Pyrolysis process was accomplished at four distinct stages which can mainly be attributed to removal of water, decomposition of hemicellulose, decomposition of cellulose, and decomposition of lignin, respectively. The activation energies, pre-exponential factors, and reaction orders of active pyrolysis stages were calculated by Arrhenius, Coats?CRedfern, and Horowitz?CMetzger model-fitting methods, while activation energies were additionaly determined by Flynn?CWall?COzawa model-free method. Average activation energies of the second and third stages calculated from model-fitting methods were in the range of 121?C187 and 320?C353?kJ?mol^?1, respectively. The FWO method yielded a compatible result (153?kJ?mol^?1) for the second stage but a lower result (187?kJ?mol^?1) for the third stage. The existence of kinetic compensation effect was evident.     

Biotechnological Utilization of Biodiesel-Derived Glycerol for the Production of Ribonucleotides and Microbial Biomass

Ten yeast strains were evaluated concerning their capabilities to assimilate biodiesel-derived glycerol in batch cultivation. The influence of glycerol concentration, temperature, pH and yeast extract concentration on biomass production was studied for the yeast selected. Further, the effect of agitation on glycerol utilization by the yeast Hansenula anomala was also studied. The yeast H. anomala CCT 2648 showed the highest biomass yield (0.30?g?g^?1) and productivity (0.19?g?L^?1?h^?1). Citric acid, succinic acid, acetic acid and ethanol were found as the main metabolites produced. The increase of yeast extract concentration from 1 to 3?g?L^?1 resulted in high biomass production. The highest biomass concentration (21?g?L^?1), yield (0.45?g?g^?1) and productivity (0.31?g?L^?1?h^?1), as well as ribonucleotide production (13.13?mg?g^?1), were observed at 700?rpm and 0.5?vvm. These results demonstrated that glycerol from biodiesel production process showed to be a feasible substrate for producing biomass and ribonucleotides by yeast species.     

Determination of tocopherol contents of some olive varieties harvested at different ripening periods

The tocopherol contents of oils obtained from Ayval?k, Domat and Gemlik olive varieties harvested at different ripening periods were evaluated by high-performance liquid chromatography. α-Tocopherol was the major tocol detected in all the studied olive oil samples. The oils extracted from olive fruits composed of 130.54-180.43?mg?kg?1 α-tocopherol, 0.73-1.61?mg?kg?1 β-tocopherol and 0.53-2.28?mg?kg?1 γ-tocopherol for Ayval?k oil. The α-, β- and γ-tocopherol contents of Domat oil are in the ranges 95.60-125.56, 0.71-2.70 and 0.49-1.25?mg?kg?1 at different harvesting periods. The α-, β- and γ-tocopherol contents of Gemlik olive oil are in the ranges 112.59-168.19, 0.94-1.21 and 0.85-2.40?mg?kg?1, respectively. There were significant differences between the oils from cultivars grown in different environments.     

Antioxidant and antiproliferative activity of Laurus nobilis L. (Lauraceae) leaves and seeds essential oils against K562 human chronic myelogenous leukaemia cells

The antioxidant and antiproliferative activities of the essential oils from Laurus nobilis leaves and seeds in relation to their composition were analysed. The most abundant components of the leaf essential oil were 1,8-cineole, 1-p-menthen-8-ethyl acetate, linalool and sabinene, while the seed oil was characterised by β-ocimene, 1,8-cineole, α-pinene and β-pinene as main constituents. Both seed and leaf essential oils exhibited a scavenging effect on the DPPH radical, with IC?? values of 66.1 and 53.5?μg?mL?1, respectively. The leaf essential oil showed the strongest antioxidant activity in the β-carotene/linoleic acid system, with an IC?? value of 35.6?μg?mL?1 after 30?min of incubation. Both leaf and seed oils inhibited proliferation of the K562 tumour cell line with IC?? values of 95 and 75?μg?mL?1, respectively. The L. nobilis leaf oil showed a percentage of erythroide differentiation of 15% at a concentration of 10?μg?mL?1. A value of 12% was found for the seed essential oil at a concentration of 50?μg?mL?1. When the oils were added to a suboptimal concentration of the commercial drug, cytosine arabinoside, a clear synergic effect was observed.     

Elemental Analysis of Tarhana by Microwave Induced Plasma Atomic Emission Spectrometry

Elemental analysis of tarhana, a traditional Turkish cereal soup, has been conducted. A new method was developed for the determination of calcium, iron, magnesium, manganese, potassium, and sodium, in tarhana by microwave induced plasma atomic emission spectrometry. A sample of 0.1?g were mineralized by microwave digestion in 10?mL of 65% HNO₃. A wheat flour standard reference material (GBW 08503) was used for validation. Linear calibration using standards prepared in acid was conducted for all determinations. The limits of detection were 1.21?µg?g^?1 for Ca at 393.366?nm, 0.43?µg?g^?1 for Fe at 259.940?nm, 11.5?µg?g^?1 for K at 766.491?nm, 0.12?µg?g^?1 for Mg at 285.213?nm, 0.04?µg?g^?1 for Mn at 403.076?nm, and 0.04?µg?g^?1 for Na at 588.995?nm. Ca, K, Fe, Mg, Mn, and Na were determined in tarhana with values from 0.73 to 1.61, 0.016 to 0.061, 2.02 to 4.09, 0.473 to 1.414, 0.019 to 0.043, and 0.26 to 1.83?mg?g^?1, respectively.     

An investigation of phenolic compounds from plant sources as trypsin inhibitors

In the search of new trypsin inhibitors caffeic acid (1), cinnamic acid (2), gallic acid (3) and eugenol (4) from Cinnamomum zeylanicum, ferulic acid (5) from Impatiens bicolor, vanillin (6) from Melia azedarach and catechol (7) from Allium cepa were isolated through bioassay guided fractionation of the plant extracts. IC (50) values of the compounds 1, 2 and 5 were found to be 0.35?±?0.02?mM, 0.96?±?0.05?mM and 1.22?±?0.06?mM, respectively. Lineweaver-Burk and Dixon plots and their secondary replots showed that 1 was non-competitive inhibitor of this enzyme with K(i) value 0.102?±?0.006?mM.     

Cholinesterase inhibition activity of Marsilea quadrifolia Linn. an edible leafy vegetable from West Bengal, India

Maesilea quadrifolia Linn. (Marsileaceae) is a leafy vegetable well known in India. The current study aims to explore the phytochemical profile of M. quadrifolia and investigate its anti-cholinesterase potential. The methanol extract of the plant was subjected to qualitative and quantitative phytochemical screening (total alkaloidal content, saponin content and phenol content) and its anti-cholinesterase potential was tested by TLC bioautography and other screening methods using acytylcholinesterase (AChE) and butyrylcholinesterase (BChE). The study revealed that the extract contains various classes of phytoconstituents including steroids, saponins, alkaloids and other polyphenols. Total alkaloid, phenolic and saponin contents were found to be 19.3?mg?g?1 and 158.5?±?1.02?mg?g?1 as gallic acid equivalents and 2.63?mg?g?1 of the extract, respectively. The TLC bioautography method exhibited the inhibition of both enzymes. In a microtiter plate assay, the IC?? values of the extract for AChE and BChE were found to be 51.89?±?0.24?μg?mL?1 and 109.43?±?2.82?μg?mL?1, respectively. These findings suggest that M. quadrifolia is a potential lead as an AChE and BChE inhibitor, which may be useful in the management of Alzheimer's disease.     

硫磺素型聚乳酸/苯磺酸室温磷光体系的构建

在硫磺素上分别引入给电子基氧、 硫和甲氧基, 合成出2-[4-(苯并噻唑-2-基)苯氧基]乙-1-醇(BT-OH)、 2-{[4-(苯并噻唑-2-基)苯基]硫代}乙-1-醇(BT-SH)和2-[4-(苯并噻唑-2-基)-2-甲氧基苯氧基]乙-1-醇(BT-M-OH) 3种硫磺素衍生物. 利用硫磺素衍生物作为引发剂引发D,L-丙交酯聚合, 得到3种硫磺素型聚乳酸, 再加入苯磺酸, 构建出可在室温下产生磷光的硫磺素型聚乳酸/苯磺酸体系, 实现了从荧光到磷光的可调分子发射, 其中磷光寿命最长达108.19 ms. 研究发现, 引入苯磺酸会使硫磺素型聚乳酸产生分子内电荷转移态, 质子化效应导致绿色和橘色的磷光发射.     

Polyoxometalate (POM)-based, multi-functional, inorganic-organic, hybrid compounds: syntheses and molecular structures of silanol- and/or siloxane bond-containing species grafted on mono- and tri-lacunary Keggin POMs

Using 3-mercaptopropyltrimethoxysilane (HS(CH?)?Si(OMe)?) as a silane-coupling agent (SCA), mono- and tri-lacunary Keggin polyoxometalate (POM)-based, multi-functional, inorganic-organic, hybrid compounds, (Et?N)?[α-PW??O??{(HS(CH?)?Si)?O}] EtN-1 (the 1?:?2 complex of a POM unit and organosilyl groups), (Bu?N)?[A-PW?O??(HS(CH?)?SiOH)?] BuN-2 (the 1?:?3 complex) and (Bu?N)?[A-α-PW?O??(HS(CH?)?SiO)?(Si(CH?)?SH)] BuN-3 (the 1?:?4 complex) were synthesized and unequivocally characterized by elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solid-state (2?Si and 31P) CPMAS NMR, solution (2?Si, 31P, 1H and 13C) NMR, and X-ray crystallography. [Note: The moieties of their polyoxoanions are abbreviated simply as 1-3, respectively.] The X-ray molecular structures of EtN-1 and BuN-3 were determined. In EtN-1, two organic groups connected through a siloxane bond (-Si-O-Si- bond) were grafted on a mono-lacunary site of a Keggin POM, whereas in BuN-3 four organic groups connected through siloxane bonds were grafted on a tri-lacunary site of a Keggin POM. In BuN-2, three organic groups were grafted in the form of silanol (-SiOH) on a tri-lacunary site, i.e., in BuN-2 there was no siloxane bond. BuN-3 was synthesized as BuN-3a and BuN-3b by two methods, respectively; (1) BuN-3a was obtained by a 1?:?1 molar-ratio reaction of BuN-2 and an SCA in CH?CN, and (2) BuN-3b was prepared by a direct 1?:?4 molar-ratio reaction of a tri-lacunary Keggin POM and SCA in water-CH?CN. X-Ray crystallography revealed that BuN-3a is the same as BuN-3b. It is probable that BuN-2 is an intermediate in the formation of BuN-3. Terminal -SH groups in 1-3, as well as -OH groups in 2, can be utilized for immobilization of POMs and, also, as building blocks for the formation of novel hybrid compounds.     

Interaction of dipropyltin(IV) with amino acids,peptides, dicarboxylic acids and DNA constituents

Interaction of dipropyltin(IV) with selected amino acids, peptides, dicarboxylic acids or DNA constituents was investigated using potentiometric techniques. Amino acids form 1?:?1 and 1?:?2 complexes and, in some cases, protonated complexes. The amino acid is bound to dipropyltin(IV) by the amino and carboxylate groups. Serine is complexed to dipropyltin(IV) with ionization of the alcoholic group. A relationship exists between the acid dissociation constant of the amino acids and the formation constants of the corresponding complexes. Dicarboxylic acids form both 1?:?1 and 1?:?2 complexes. Diacids forming five- and six-membered chelate rings are the most stable. Peptides form complexes with stoichiometric coefficients 111(MLH), 110(ML) and 11-1(MLH_?1)(tin: peptide: H⁺). The mode of coordination is discussed based on existing data and previous investigations. DNA constituents inosine, adenosine, uracil, uridine, and thymine form 1?:?1 and 1?:?2 complexes and the binding sites are assigned. Inosine 5′-monophosphate, guanosine 5′-monophosphate, adenosine 5′-monophosphate and adenine form protonated species in addition to 1?:?1 and 1?:?2 complexes. The protonation sites and tin-binding sites were elucidated. Cytosine and cytidine do not form complexes with dipropyltin(IV) due to low basicity of the donor sites. The stepwise formation constants of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD-75. The concentration distribution of the various complex species was evaluated as a function of pH.