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71.
72.
《Journal of Coordination Chemistry》2012,65(2):193-206
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. 相似文献
73.
《Journal of Coordination Chemistry》2012,65(1-3):17-23
The DNA cleavage properties of two cationic manganese porphyrins possessing different peripheral substituents were compared. The identical nature of the strand scission patterns of the porphyrins on a 139 base pair restriction fragment of pBR-322 DNA, along with other evidence, suggests that the porphyrin is end-on bound via the minor groove in a melted or partially melted region of DNA. This unusual binding mode underscores the potential of outisde binding cationic metalloporphyrins as probes for low melting regions of DNA 相似文献
74.
Dr. Renata Kaczmarek Samuel Ward Dipra Debnath Taisiya Jacobs Alexander D. Stark Dariusz Korczyński Prof. Dr. Anil Kumar Prof. Dr. Michael D. Sevilla Dr. Sergey A. Denisov Dr. Viacheslav Shcherbakov Dr. Pascal Pernot Prof. Dr. Mehran Mostafavi Prof. Dr. Roman Dembinski Prof. Dr. Amitava Adhikary 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(43):9495-9505
The directionality of the hole-transfer processes between DNA backbone and base was investigated by using phosphorodithioate [P(S−)=S] components. ESR spectroscopy in homogeneous frozen aqueous solutions and pulse radiolysis in aqueous solution at ambient temperature confirmed initial formation of G.+-P(S−)=S. The ionization potential of G-P(S−)=S was calculated to be slightly lower than that of guanine in 5′-dGMP. Subsequent thermally activated hole transfer from G.+ to P(S−)=S led to dithiyl radical (P-2S.) formation on the μs timescale. In parallel, ESR spectroscopy, pulse radiolysis, and density functional theory (DFT) calculations confirmed P-2S. formation in an abasic phosphorodithioate model compound. ESR investigations at low temperatures and higher G-P(S−)=S concentrations showed a bimolecular conversion of P-2S. to the σ2-σ*1-bonded dimer anion radical [-P-2S 2S-P-]− [ΔG (150 K, DFT)=−7.2 kcal mol−1]. However, [-P-2S 2S-P-]− formation was not observed by pulse radiolysis [ΔG° (298 K, DFT)=−1.4 kcal mol−1]. Neither P-2S. nor [-P-2S 2S-P-]− oxidized guanine base; only base-to-backbone hole transfer occurs in phosphorodithioate. 相似文献
75.
Nikolaus Krall Dr. Jörg Scheuermann Prof. Dario Neri 《Angewandte Chemie (International ed. in English)》2013,52(5):1384-1402
The targeted delivery of potent cytotoxic agents has emerged as a promising strategy for the treatment of cancer and other serious conditions. Traditionally, antibodies against markers of disease have been used as drug‐delivery vehicles. More recently, lower molecular weight ligands have been proposed for the generation of a novel class of targeted cytotoxics with improved properties. Advances in this field crucially rely on efficient methods for the identification and optimization of organic molecules capable of high‐affinity binding and selective recognition of target proteins. The advent of DNA‐encoded chemical libraries allows the construction and screening of compound collections of unprecedented size. In this Review, we survey developments in the field of small ligand‐based targeted cytotoxics and show how innovative library technologies will help develop the drugs of the future. 相似文献
76.
77.
Mercury film plated on a glassy carbon electrode modified with multiwalled carbon nanotubes (MF/MWNTs/GCE) was used for the analysis of single (ss) and double stranded (ds) DNA, as well as for Jurkat genomic DNAs methylated to different degrees. The results indicated that the DNA molecules adsorbed quite strongly on the MF/MWNTs/GCE surface allowing ex situ adsorption and produce well developed peaks (due to cytosine and adenine) by using adsorptive stripping (Ads, ex situ) square wave voltammetry (SWV). Also, SWV of Jurkat DNA mixtures methylated to different degrees revealed a linear decrease of the peak height with increasing methylation indicating an increase of structural rigidity. 相似文献
78.
This numerical study provides an error analysis of an idealized nanopore sequencing method in which ionic current measurements are used to sequence intact single‐stranded DNA in the pore, while an enzyme controls DNA motion. Examples of systematic channel errors when more than one nucleotide affects the current amplitude are detailed, which if present will persist regardless of coverage. Absent such errors, random errors associated with tracking through homopolymer regions are shown to necessitate reading known sequences (Escherichia coli K‐12) at least 140 times to achieve 99.99% accuracy (Q40). By exploiting the ability to reread each strand at each pore in an array, arbitrary positioning on an error rate versus throughput tradeoff curve is possible if systematic errors are absent, with throughput governed by the number of pores in the array and the enzyme turnover rate. 相似文献
79.
Dr. Anna‐Barbara Gerber Prof. Christian J. Leumann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(22):6990-7006
We present the synthesis of the isobicyclo‐DNA building blocks with the nucleobases A, C, G and T, as well as biophysical and biological properties of oligonucleotides derived thereof. The synthesis of the sugar part was achieved in 5 steps starting from a known intermediate of the tricyclo‐DNA synthesis. Dodecamers containing single isobicyclo‐thymidine incorporations, fully modified A‐ and T‐containing sequences, and fully modified oligonucleotides containing all four bases were synthesized and characterized. Isobicyclo‐DNA forms stable duplexes with natural nucleic acids with a pronounced preference for DNA over RNA as complements. The most stable duplexes, however, arise by self‐pairing. Isobicyclo‐DNA forms preferentially B‐DNA‐like duplexes with DNA and A‐like duplexes with complementary RNA as determined by circular dichroism (CD) spectroscopy. Self‐paired duplexes show a yet unknown structure, as judged from CD spectroscopy. Biochemical tests revealed that isobicyclo‐DNA is stable in fetal bovine serum and does not elicit RNaseH activity. 相似文献
80.
Fluorescent nucleosides and oligonucleotides functionalized with pyrene were synthesized using ‘click’ chemistry or the Sonogashira cross-coupling reaction. The dye was connected to position-7 of 7-deaza-2′-deoxyguanosine or to the 2′-deoxyribofuranose moiety. Four different DNA-dye connectors with 1,2,3-triazolyl residues or triple bonds were constructed. Phosphoramidites of the pyrene conjugates (9, 14, 25) were prepared and used in solid-phase synthesis. Short linkers (2, 4) destabilize DNA, while long linkers (1) increased duplex stability. Nucleosides and oligonucleotides with single dye incorporations show linker dependent fluorescence. Linker dependent excimer emission with pyrenes in proximal positions was also observed. A ‘superchromophore’ formed by the 7-deaza-2′-deoxyguanosine ethynylpyrene conjugate shows strong red shifted fluorescence emission at 495 nm. 相似文献