Electrophoretic extraction and analysis of DNA from chitosan or poly-l-lysine-coated alginate beads

Alginate beads containing entrapped DNA were produced using both external and internal calcium sources, and coated with chitosan or poly-l-lysine membranes. The beads were assayed with DNase nuclease to determine formulation conditions offering the highest level of DNA protection fromnucleic acid hydrolysis, simulating gastrointestinal exposure. A method was developed to extract and assay intracapsular DNA through a modified agarose electrophoresis system. Both external and internally gelled beads were permeable to DNase (M_w=31 kDa), indicated by the absence of DNA after nuclease exposure. At low levels of DNase exposure, coated high guluronic content alginate beads offered a higher level of DNA protection compared with coated beads with low guluronic alginate. No apparent correlation was found with chitosan membrane molecular weight and degree of deacetylation; however, increasing poly-l-lysine molecular weight appeared to increase DNase exclusion from beads. At elevated levels of DNase exposure, DNA hydrolysis was evident within all coated beads with the exception of those coated with the highest molecular weight poly-l-lysine (M_w=197.1 kDa), which provided almost total nuclease protection. Optimal combination then for DNA protection from nucleases is a high guluronic alginate core, coated with high molecular weight poly-l-lysine.     

金属蛋白研究中几个值得注意的动向

本文叙述了金属蛋白和金属酶研究中近年来几个值得注意的发展动向，即与金属离子相关的疾病（特别是神经退行性疾病）、金属离子在蛋白质的折叠、聚集和装配中的作用，金属伴侣分子、金属蛋白的设计和构建、金属蛋白与DNA相互作用。     

The 2-(4-trifluoromethylphenylsulfonyl)ethoxycarbonyl (Tsc) amino-protecting group: use in the solid-phase synthesis of pyrrole-imidazole polyamides

The development of the 2-(4-trifluoromethylphenylsulfonyl)ethoxycarbonyl (Tsc) function, a novel base-sensitive amino-protecting group, and its application to the preparation of DNA-binding polyamides are described. Pyrrole-imidazole polyamides were synthesized by an efficient solid-phase method under conditions compatible with Fmoc chemistry using two Tsc-protected amino acids, Tsc-Py-OH 1a and Tsc-Im-OH 1b.     

DNA codes for nanoscience

The nanometer scale is a special place where all sciences meet and develop a particularly strong interdisciplinarity. While biology is a source of inspiration for nanoscientists, chemistry has a central role in turning inspirations and methods from biological systems to nanotechnological use. DNA is the biological molecule by which nanoscience and nanotechnology is mostly fascinated. Nature uses DNA not only as a repository of the genetic information, but also as a controller of the expression of the genes it contains. Thus, there are codes embedded in the DNA sequence that serve to control recognition processes on the atomic scale, such as the base pairing, and others that control processes taking place on the nanoscale. From the chemical point of view, DNA is the supramolecular building block with the highest informational content. Nanoscience has therefore the opportunity of using DNA molecules to increase the level of complexity and efficiency in self-assembling and self-directing processes.     

Thermodynamics of formation of nitrogen bases and d-ribose from mineral substances in light of the problem of origination of simplest elements of living matter

The paper represents a further development of our hydrate hypothesis of simplest living matter origination (SLMO) from inorganic and simplest organic mineral substances. It is supposed that the sources of SLMO are simplest aliphatic hydrocarbons, niters, and phosphates. Thermodynamic calculations demonstrating a principal possibility for simultaneous syntheses of different nitrogen bases, d-ribose, and desoxy-d-ribose from these source substances are presented. The most probable principal mechanism of SLMO and the principal conditions necessary for realization of the proposed chemism of SLMO in the framework of the proposed mechanism are considered. A principal means for testing the hypothesis is proposed.     

Determination of DNA using sodium 9,10-anthraquinone-2-sulfonate as an in situ photochemical fluorescence probe

An in situ photochemical fluorescence probe method for the determination of DNA with sodium 9,10-anthraquinone-2-sulfonate (AQS) as a photochemical fluorescence probe was developed. It was based on the conversion of AQS into an intensively fluorescent product by irradiating with UV radiation. The photochemical reaction is retarded by DNA. The determination can be carried out by measuring the fluorescence intensity at a fixed time. The calibration graph was linear in the range 0–80 ng ml⁻¹ calf thymus (CT) DNA (r = 0.9991), the limit of detection was 3.2 ng ml⁻¹ CT DNA (n = 9). The kinetic behaviour of the photochemical reaction and the effects of experimental conditions were investigated and discussed in detail. The results of absorption spectra and competitive binding experiments suggested the interaction between AQS and DNA to be intercalative.     

Effect of DNA and bivalent metal ions on the interaction of thermostable DNA polymerase <Emphasis Type="Italic">Tte</Emphasis> with dNTPs

The interaction of DNA polymerase Tte from Thermus thermophilus B35 with dUTP analog containing a fluorescein residue bound to C(5) of the base (Flu-dUTP) was studied by fluorescence titration. The dissociation constants of the enzyme—substrate complexes in the absence and in the presence of a DNA duplex containing an extended template and bivalent metal ions and the kinetic parameters of polymerization by DNA polymerase Tte in the presence of Flu-dUTP were determined. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1268–1272, May, 2005.     

Lewis acid deprotection of silyl-protected oligonucleotides and base-sensitive oligonucleotide analogues

Oligonucleotides protected with N-(trimethylsilylethoxycarbonyl) (Teoc) and P-(trimethylsilylethanol) (Tse) groups were synthesized and deprotected by a single ZnBr₂ treatment. Teoc group stabilized dA against depurination. This strategy was applied to the synthesis of base-sensitive oligonucleotide prodrugs bearing S-acetyl-2-thioethyl (Sate) phosphotriesters.     

Enhancing effect of DNA on chemiluminescence from the decomposition of hydrogen peroxide catalyzed by copper(II)

In the absence of any special luminescence reagent, emission of weak chemiluminescence has been observed during the decomposition of hydrogen peroxide catalyzed by copper(II) in basic aqueous solution. The intensity of the chemiluminescence was greatly enhanced by addition of DNA and was strongly dependent on DNA concentration. Based on these phenomena, a flow-injection chemiluminescence method was established for determination of DNA. The chemiluminescence intensity was linear with DNA concentration in the range 2×10^–7–1×10^–5 g L^–1 and the detection limit was 4.1×10^–8 g L^–1 (S/N=3). The relative standard deviation was less than 3.0% for 4×10^–7 g L^–1 DNA (n=11). The proposed method was satisfactorily applied for determination of DNA in synthetic samples. The possible mechanism of the CL reaction is discussed.