Targeting abasic sites and single base bulges in DNA with metalloinsertors

The site-specific recognition of abasic sites and single base bulges in duplex DNA by sterically expansive rhodium metalloinsertors has been investigated. Through DNA photocleavage experiments, Rh(bpy)2(chrysi)3+ is shown to bind both abasic sites and single base bulges site-specifically and, upon irradiation, to cleave the backbone of the defect-containing DNA. Photocleavage titrations reveal that the metal complex binds DNA containing an abasic site with high affinity (2.6(5) x 106 M-1), comparably to the metalloinsertor and a CC mismatch. The complex binds single base bulge sites with lower affinity (approximately 105 M-1). Analysis of cleavage products and the correlation of affinities with helix destabilization suggest that Rh(bpy)2(chrysi)3+ binds both lesions via metalloinsertion, as observed for Rh binding at mismatched sites, a binding mode in which the mismatched or unpaired bases are extruded from the helix and replaced in the base stack by the sterically expansive ligand of the metalloinsertor.     

Dynamics and supramolecular organization of the 1D spin transition polymeric chain compound [Fe(NH2trz)3](NO3)2. Muon spin relaxation

The thermal spin transition that occurs in the polymeric chain compound [Fe(NH(2)trz)3](NO3)2 above room temperature has been investigated by zero-field muon spin relaxation (microSR) over the temperature range approximately 8-402 K. The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components, respectively. The spin transition is associated with a hysteresis loop of width DeltaT = 34 K (T1/2 upward arrow = 346 K and T1/2 downward arrow = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter, in good agreement with previously published magnetic measurements. Zero-field and applied field (20-2000 Oe) microSR measurements show the presence of diamagnetic muon species and paramagnetic muonium radical species (A = 753 +/- 77 MHz) over the entire temperature range. Fast dynamics have been revealed in the high-spin state of [Fe(NH(2)trz)3](NO3)2 with the presence of a Gaussian relaxation mode that is mostly due to the dipolar interaction with static nuclear moments. This situation, where the muonium radicals are totally decoupled and not able to sense paramagnetic fluctuations, implies that the high-spin dynamics fall outside the muon time scale. Insights to the origin of the cooperative effects associated with the spin transition of [Fe(NH(2)trz)3](NO3)2 through muon implantation are presented.     

Purification of deoxynivalenol from Fusarium graminearum rice culture and mouldy corn by high-speed counter-current chromatography

Deoxynivalenol (DON) is a mycotoxin produced by several Fusarium species and is toxic to a wide range of organisms, including human beings and livestock. To produce large amounts of pure DON for research purposes, a novel method using high-speed counter-current chromatography (HSCCC) was developed. Rice cultured with Fusarium graminearum and field mouldy corn infected by F. graminearum were extracted with methanol and found to contain 1.16 and 1.30 mg DON/g, respectively. The extracts were concentrated and then separated using a biphasic solvent system consisting of ethyl acetate-water (1:1, v/v). Collected fractions were analyzed by high-performance liquid chromatography (HPLC) and identified by congruent retention time and UV/vis spectrum and mass spectrometric data. Fractions containing DON were combined and freeze-dried. This method produced 116 mg and 65 mg DON with a purity of greater than 94.9% from 200 g of the rice culture and the mouldy corn, respectively. The HSCCC method had a recovery rate of DON at 88% from the crude extracts of both samples. This one-step purification method provided a simple and effective tool for obtaining a large amount of DON, an essential material for studies related to toxicology and detoxification of this mycotoxin.     

Selective thin-layer chromatography of 4-R-1,2,4-triazoles

A convenient and selective TLC of 4-R-1,2,4-triazoles (Rtrz) and nitrogen containing aromatic rings is presented (molecules 1-11). This simple revelation method implies a complexation of heterocycles to Co(II) ions on a TLC plate, followed by a subsequent modification of the reduction potential which enables oxidation of Co(II) by permanganate.     

Efficient generation of a trisporoid library by combination of synthesis and biotransformation

Trisporic acids and their biosynthetic precursors represent a family of powerful fungal pheromones and morphogenetic factors. A highly flexible synthetic protocol is described that (i) provides rapid access to nonfunctionalized early trisporoids from beta-ionone, (ii) includes a regiospecific oxidative functionalization of beta-ionone leading to 1-acetoxy-beta-ionone giving access to functionalized trisporoids, and (iii) utilizes a biotransformation of early synthetic trisporoids by growing cells of Blakeslea trispora to prepare late trisporoids including trisporic acids. The same protocol also provides deuterium-labeled trisporoids such as trisporin B [2H3]-19. Administration of [2H3]-19 to growing cells of the (-)-mating type of B. trispora resulted in the formation of the labeled trisporols [2H3]-20 and [2H3]-21. Growing cultures containing both mating types can be used to prepare trisporic acids from early precursors.     

多核羰基钴配合物的合成及其催化活性的研究

多核羰基钴配合物对很多有机化学反应有良好的催化作用,从而引起人们很大关注.但这类配合物由高压反应得到,因此给实用带来不便. 我们通过各种含膦配体的氯化钴,在锌粉存在下,与一氧化碳在常温常压下反应,得到了一系列通式为:(PR_3)_mCo_n(CO)_x的多核羰基钴配合物,讨论了它们的结构,并对这些配合物在由十四碳烯羰基合成作为表面活性剂原料的十五碳伯醇反应中的催化性能进行了研究.     

光度法测定松脂中的铝

研究了用铝试剂,乙酸－乙酸铵缓冲溶液组织的体系以及光度法测定松脂微量铝的条件,提出了一种灵敏度、选择性与稳定性较好的测定松脂中铝的方法,在０－５０μｇ／５０ｍＬ范围内服从比耳定律。     

Mevalonate-Independent Biosynthesis of Terpenoid Volatiles in Plants: Induced and Constitutive Emission of Volatiles

Terpenoids from flower and leaf volatiles are predominantly synthesized along the mevalonate-independent pathway, as shown by administration of [D₂]deoxy-D -xylulose and [D₅]mevalolactone. The parallel use of two pathways for the biosynthesis of the sesquiterpenoid-derived 4,8-dimethylnona-1,3,7-triene (DMNT, see picture) may be important to ensure the synthesis of the volatile alarm codes of plants.