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1.
Anna Kobyláska Andrzej Okruszek Wojciech J. Stec 《Nucleosides, nucleotides & nucleic acids》2013,32(9-11):1977-1982
Abstract 2-Thiono-1,3,2-oxathiaphospholane derivatives of lipophilic alcohols including borneol, cholesterol, menthol and heptadecanol were synthesized and reacted with support-bound oligodeoxyribonucleotides containing free 5′-hydroxyl groups. The reaction is catalyzed by DBU and leads to oligodeoxyribonucleotide conjugates possessing a lipophilic alcohol residue bound at the 5′-end via a phosphorothioate linkage. 相似文献
2.
The objective of this study is to understand the influence of pH and effect of cosolvent (glucose) on the stabilization of bovine α-lactalbumin by using ultrasonic techniques. Values of density, ultrasonic velocity and viscosity were measured for bovine α-lactalbumin (5 mg/ml) dissolved in phosphate buffer (pH 2, 5, 7, 9 and 12) solutions mixed with and without the cosolvent at 30 °C. These measurements were used to calculate few thermo-acoustical parameters such as adiabatic compressibility, intermolecular free length, acoustic impedance, relaxation time, relative association constant, the partial apparent specific volume and the partial apparent specific adiabatic compressibility for the said systems. The obtained results revealed a strong comparison between the effects of acidic and alkaline pH values on protein denaturation, i.e., the acidic pH are instantaneous and are of less magnitude whereas alkaline pH are slower but sharper. Further the present study supports the fact that the presence of glucose stabilizes α-lactalbumin against denaturation due to pH variation, which may be due to the strengthening of non-covalent interactions and the steric exclusion effect. 相似文献
3.
Prasanna Jayalath Subhash Pokharel Eduardo Véliz Peter A. Beal 《Nucleosides, nucleotides & nucleic acids》2013,32(2):78-88
The RNA-editing adenosine deaminases (ADARs) catalyze deamination of adenosine to inosine in double stranded structure found in various RNA substrates, including mRNAs. Here we describe the synthesis of a phosphoramidite of 2 ′-deoxy-2 ′-mercaptoadenosine and its incorporation into an ADAR substrate. Surprisingly, no deamination product was observed with this substrate indicating replacing the 2 ′-OH with a 2 ′-SH at the editing site is highly inhibitory. Modeling of nucleotide binding into the active site suggests the side chain of T375 of human ADAR2 to be in proximity of the 2 ′-substituent. Mutation of this residue to cysteine caused a greater that 100-fold reduction in deamination rate with the 2 ′-OH substrate. 相似文献
4.
summary. A thermostable -amylase from B. licheniformis (BLA) and a mesophilic amylase from B. amyloliquefaciens (BAA) were covalently coupled to oxidized synthetic sucrose polymers (OSP400 and OSP70) and polyglutaraldehyde (PGA) by reductive alkylation to study the effect of neoglycosylation on the activity, kinetic and thermodynamic stability. The catalytic efficiency of the modified enzymes was comparable to that of the native enzyme. Covalent coupling decreased the rate of inactivation at all the temperatures studied, both in the presence and absence of added Ca2+. The stability of the native enzyme was found to increase upon modification as observed from the increase in t1/2 in the absence of Ca2+ ions by about 1.5–13.7 times (at 85°C) in the case of BLA and 5.7–8.4 times (at 50°C) for BAA. The highest stability was observed for OSP400 modified enzyme with Cm and Tm values of 0.63 M and 7.92°C for BLA and 0.85 M and 5.3°C for BAA, respectively. The order of stability was OSP400 > OSP70 > PGA > Native for both BLA and BAA. The stability of the modified amylases obtained from the present study were superior compared to most of the single and double mutants obtained by site-directed mutagenesis that were constructed so as to enhance the intrinsic stability of these enzymes.This article is dedicated to Dr. P.V. Sundaram. 相似文献
5.
Paula L. Fischhaber Annabelle W. Reese Thuc Nguyen James J. Kirchner Eric J. Hustedt Bruce H. Robinson 《Nucleosides, nucleotides & nucleic acids》2013,32(4):365-377
Abstract We report the chemical synthesis of phosphoramidite 8, containing a spin labeled analog of deoxycytidine, C?, and its incorporation into synthetic DNA. The EPR characteristics of the resulting DNAs indicated that the motion of the spin label was well-correlated with the uniform modes of the macromolecule, but that correlation of the spin label with internal motion was less effective than that achieved using a spin labeled quinolone, Q. 相似文献
6.
Yousefi R Imani M Ardestani SK Saboury AA Gheibi N Ranjbar B 《Acta biochimica et biophysica Sinica》2007,39(10):795-802
Calprotectin, a heterodimeric complex belonging to the S 100 protein family, has been found predominantly in the cytosolic fraction of neutrophils. In the present study, human calprotectin was purified from neutrophils using two-step ion exchange chromatography. The purified protein was used for circular dichroism study and fluorescence analysis in the presence of calcium and zinc at physiological concentrations, as well as for assessment of its inhibitory activity on the K562 leukemia cell line. The thermal stability of the protein at pH 7.0 (physiological pH) and 8.0 (similar to intestinal pH) was also compared. The results of cell proliferation analysis revealed that human calprotectin initiated growth inhibition of the tumor cells in a dose- dependent manner. The intrinsic fluorescence emission spectra of human calprotectin (50 ktg/ml) in the presence of calcium and zinc ions show a reduction in fluorescence intensity, reflecting a conformational change within the protein with exposure of aromatic residues to the protein surface that is important for the biological function of calprotectin. The far ultraviolet-circular dichroism spectra of human calprotectin in the presence of calcium and zinc ions at physiological concentrations show a decrease in the m-helical content of the protein and an increase in [3- and other structures. Our results also show that increasing the pH level from 7.0 to 8.0 leads to a marked elevation in the thermal stability of human calprotectin, indicating a significant role for pH in the stability of calprotectin in the gut. 相似文献
7.
Anilkumar R. Kore Bo Yang Balasubramanian Srinivasan Annamalai Senthilvelan 《Nucleosides, nucleotides & nucleic acids》2015,34(1):33-39
We describe concise and efficient synthesis of biologically very important 3′-O-tetraphosphates namely 2′-deoxyadenosine-3′-O-tetraphosphate (2′-d-3′-A4P) and 2′-deoxycytidine-3′-O-tetra-phosphate (2′-d-3′-C4P). N6-benzoyl-5′-O-levulinoyl-2′-deoxyadenosine was converted into N6-benzoyl-5′-O-levulinoyl-2′-deoxyadenosine-3′-O-tetraphosphate in 87% yield using a one-pot synthetic methodology. One-step concurrent deprotection of N6-benzoyl and 5′-O-levulinoyl groups using concentrated aqueous ammonia resulted 2′-d-3′-A4P in 74% yield. The same synthetic strategy was successfully employed to convert N4-benzoyl-5′-O-levulinoyl-2′-deoxycytidine into 2′-d-3′-C4P in 68% yield. 相似文献
8.
Takeshi Wada Naotake Kobayashi Toshiya Mori Mitsuo Sekine 《Nucleosides, nucleotides & nucleic acids》2013,32(1-3):351-364
Abstract Diastereoselective formation of internucleotidic phosphorothioate triester bonds was achieved by use of 3-(imidazol-1-ylmethyl)-4′,4″-dimethoxytrityl (IDTr) as a 5′-hydroxyl protecting group in the phosphotriester approach. After removal of all the protecting groups, stereochemistry of the major product was determined as the Spconfiguration by enzymatic digestion. 相似文献
9.
10.
Abstract 3-β-D-Ribofuranosylpyazolo[4,3-d]pyrimidines (formycins)1 modified in the heteroaromatic moiety are of biological interest as analogues of adenosine and guanosine, and have been the objects of intensive synthetic chemical effort by several groups.2-9 2′-Deoxynucleosides2c,2d,7b,13 and other analogties of the formycins modified in the sugar moiety10-12 are also of potential interest, but have been less extensively studied. Examples of the 2′-deoxyribonucleoside type known to date include the 2′-deoxy-6-thioguanosine analogue 1, the 2′-deoxyadenosine (dAdo) analogue 2 (2′-deoxyformycin A),10,13 and the 2-chloro-2′-deoxyadenosine analogue 3.7b Compound 2 was found to be 10-15 times more potent than 2′-deoxyadenosine as an inhibitor of the growth of S49 cells, a murine lymphoma line of T-cell origin.13 Activity depended on 5′- phosphorylation, since mutants lacking the enzymes adenosine kinase (AK) and deoxycytidine kinase (dCK) were insensitive to the drug. Furthermore, activity was comparable in the presence and absence of an AK inhibitor, suggesting that 2, unlike dAdo, may be a poor substrate for adenosine deaminase. That 5′-phosphorylation of 2 was mediated by AK rather than dCK was indicated by the fact that miitants lacking only dCK retained sensitivity. This contrasted with the behavior of dAdo, which is known to be n substrate for both AK and dCK.14 相似文献
11.
Daniela Pandolfi Francesca Rauzi Massimo L. Capobianco 《Nucleosides, nucleotides & nucleic acids》2013,32(9):2051-2069
Abstract Synthetic oligonucleotides are increasingly used because of their potential activity as regulators of gene expression. One of their major drawbacks is instability toward nucleases, in particular exonucleases. In this article, we studied some terminal modifications that can enhance exonuclease resistance, such as end-capping with alkylic chains (1,3-propanediol and 1,6-hexanediol), and with a modified nucleotide (2′,3′ -secouridine). These compounds were compared with the parent (natural) oligodeoxynucleotide and with different analogs containing a progressive number of phosphorothioate linkages. The resistance toward SVPDE and CSPDE (a 3′ - and a 5′ -exonuclease) was assessed, in vitro, by two independent techniques, UV and HPLC. Our results showed that the stability of all the modified oligonucleotides was at least 12 times that of the parent compound. 相似文献
12.
Schwartz AM Komarova TV Skulachev MV Zvereva AS Dorokhov IuL Atabekov JG 《Biochemistry. Biokhimii?a》2006,71(12):1377-1384
Eukaryotic mRNAs that prematurely terminate translation are recognized and degraded by nonsense mediated decay (NMD). This degradation pathway is well studied in animal and yeast cells. The data available imply that NMD also takes place in plants. However, the molecular mechanism of recognition and degradation of plant RNAs containing premature terminator codon (PTC) is not known. Here we report that in plant cells this mechanism involves the recognition of the sizes of the 3'-untranslated regions (3'UTR). Plant 3'UTRs longer than 300 nucleotides induce mRNA instability. Contrary to mammalian and yeast cells, this destabilization does not depend on the presence of any specific sequences downstream of the terminator codon. Unlike nuclear-produced mRNAs, plant virus vector long 3'UTR-containing RNAs, which are synthesized directly in the cytoplasm, are stable and translated efficiently. This shows that RNAs produced in the cytoplasm by viral RNA-dependent RNA polymerase are able to avoid the proposed mechanism. 相似文献
13.
α-Crystallin functions as a molecular chaperone and maintains transparency of eye lens by protecting other lens-proteins.
Non-enzymatic glycation of α-crystallin by methylglyoxal, plays a crucial role on its chaperone function and structural stability.
Our studies showed that methylglyoxal modification even in lower concentration caused significant decrease in chaperone function
of α-crystallin as reflected both in thermal aggregation assay and enzyme refolding assay. Thermal denaturation studies showed
drastic reduction of denaturation temperature with increase in the degree of modification. Thermodynamic stability studies
by urea denaturation assay reflected a decrease of transition midpoint. Quantitatively we found that ΔG° of native α-crystallin
decreased from 21.6 kJ/mol to 10.4 kJ/mol due to 72 h modification by 10 mM methylglyoxal. The surface hydrophobicity of α-crystallin
after MG modification, was found to be decreased. Circular dichroism spectroscopy revealed conversion of β-sheet structure
to random coil structure. Significant cross-linking was also observed due to methylglyoxal modification of human α-crystallin. 相似文献
14.
《Nucleosides, nucleotides & nucleic acids》2013,32(12):2195-2202
Abstract 3′-C-Trifluoromethyl-β-D-ribonucleoside derivatives bearing the five naturally occurring nucleic acid bases have been synthesized. All these derivatives were prepared by glycosylation reactions of purine and pyrimidine bases with a suitable peracylated 3-C-trifluoromethyl ribofuranose precursor. After deprotection, the resulting title nucleoside analogues were tested for their inhibitory properties against the replication of HIV, HBV and several RNA viruses. However, none of these compounds showed significant antiviral activity. 相似文献
15.
Ryszard Kierzek Wojciech T. Markiewicz 《Nucleosides, nucleotides & nucleic acids》2013,32(1-2):403-405
Abstract 5′3′-O-protected 4-N-tosyl-2′-deoxycyt id ine was converted with 1,6-diaminohexane to 4-N-/6-ami nohexyl/-2′-deoxycyt id i ne and then into 5′-0-d imethoxytr i ty 1 -k-N-/(-tr if luoroacetamidohexyl 1–2 ′-deoxycyt id ine, The latter was used to prepare oligonucleotides by the phosphoramidite approach. Deprotected oligomers were labeled with biotin. 相似文献
16.
Mikko Oivanen Ekaterina V. Efimtseva Sergey N. Mikhailov 《Nucleosides, nucleotides & nucleic acids》2013,32(8):1325-1331
Abstract The first-order rate constants for hydrolysis of 3′-C-methyluridylyl(2′,5′)- and -(3′,5′)adenosine and the corresponding native dinucleoside monophosphates (2′,5′- and 3′,5′-UpA) have been determined as a function of hydroxide-ion concentration (0.025 - 7 M) at 25°C. In addition to the effects on the hydrolytic stability of the compounds, the effects of the 3′-C-methyl substitution on the kinetically determined pK a values for the sugar hydroxyls of the undine moiety are discussed. 相似文献
17.
Yoshihito Ueno Makiko Kanazaki Satoshi Shuto Akira Matsuda 《Nucleosides, nucleotides & nucleic acids》2013,32(6-7):1401-1402
Abstract To find the nuclease-resistant oligodeoxynucleotides (ODNs) with natural phosphodiester linkages, we designed and synthesized ODNs containing 4′-C-aminoalkylthymidines (1–4). We found that the ODNs containing 1, 2, 3 or 4 were more resistant to nucleolytic hydrolysis by both snake venom phosphodiesterase (a 3′-exonuclease) and DNase I (an endonuclease) than unmodified ODNs. 相似文献
18.
Xiao Liu Xueliang Xia Chenghai Sun Cai Lin Yiqian Zhou Muzammal Hussain 《Nucleosides, nucleotides & nucleic acids》2016,35(9):479-494
The preparation of 2′-deoxy-2′-siprodifluorocyclopropany-lnucleoside analogs has been achieved from α-d-glucose in several steps. The key step in the synthesis was the introduction of the difluorocyclopropane through a difluorocarbene type reaction at the 2′-position. Then, a series of novel 2′-deoxy-2′-spirodifluorocyclopropanyl nucleoside analogs were synthesized using the Vorbrüggen method. All the synthesized nucleosides were characterized and subsequently evaluated against hepatitis C and influenza A virus strains in vitro. 相似文献
19.
《Nucleosides, nucleotides & nucleic acids》2013,32(5-8):1119-1121
Abstract C8-Arylamine-dG adducts were synthesized by palladium-catalyzed cross- coupling reactions. The corresponding 5′-O-DMTr-3′-O-phosphoramidite-C8-arylamine-dG adducts were synthesized as potential building blocks for the automated synthesis of site-specifically modified oligonucleotides. 相似文献
20.
The objective of the present study was to synthesize monomethoxypolyethyleneglycol-5000 cholesteryl ester [PEG–CH] as a cost-effective
substitute for polyethyleneglycol–phosphatidylethanolamine and to evaluate the influence of its incorporation in liposomal
bilayers for surface modification. PEG–CH was synthesized and characterized by infrared (IR), proton nuclear magnetic resonance
spectroscopy (1H NMR), and differential scanning calorimetry (DSC) studies. Influence of incorporation of PEG–CH in liposomes was evaluated
on various parameters such as zeta potential, DSC, and encapsulation efficiency of a hydrophilic drug pentoxyfylline. Conventional
and PEG–CH containing pentoxyfylline liposomes were formulated and their stability was evaluated at 4°C for 3 months. PEG–CH
could be successfully synthesized with good yields and the structure was confirmed by IR, DSC, and 1H NMR. The incorporation of PEG–CH in liposomes resulted in reduction of the zeta potential and broadening of the DSC endotherm.
Furthermore, incorporation of PEG–CH in liposomes decreased the encapsulation efficiency of pentoxifylline in liposomes when
compared to conventional liposomes. Conventional and PEG–CH containing pentoxyfylline liposomes did not show any signs of
pentoxyfylline degradation when stored at 4°C for 3 months. 相似文献