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1.
Of all the commercially available amino acid derivatives for solid phase peptide synthesis, none has a greater abundance of side‐chain protection diversity than cysteine. The high reactivity of the cysteine thiol necessitates its attenuation during peptide construction. Moreover, the propensity of cysteine residues within a peptide or protein sequence to form disulfide connectivity allows the opportunity for the peptide chemist to install these disulfides iteratively as a post‐synthetic manipulation through the judicious placement of orthogonal pairs of cysteine S‐protection within the peptide's architecture. It is important to continuously discover new vectors of deprotection for these different blocking protocols in order to achieve the highest degree of orthogonality between the removal of one species in the presence of another. We report here a complete investigation of the scope and limitations of the deprotective potential of 2,2′‐dithiobis(5‐nitropyridine) (DTNP) on a selection of commercially available Cys S‐protecting groups. The gentle conditions of DTNP in a TFA solvent system show a remarkable ability to deprotect some cysteine blocking functionality traditionally removable only by more harsh or forcing conditions. Beyond illustrating the deprotective ability of this reagent cocktail within a cysteine‐containing peptide sequence, the utility of this method was further demonstrated through iterative disulfide formation in oxytocin and apamin test peptides. It is shown that this methodology has high potential as a stand‐alone cysteine deprotection technique or in further manipulation of disulfide architecture within a more complex cysteine‐containing peptide template. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
2.
We previously reported on a method for the facile removal of 4‐methoxybenzyl and acetamidomethyl protecting groups from cysteine (Cys) and selenocysteine (Sec) using 2,2′‐dithiobis‐5‐nitropyridine dissolved in trifluoroacetic acid, with or without thioanisole. The use of this reaction mixture removes the protecting group and replaces it with a 2‐thio(5‐nitropyridyl) (5‐Npys) group. This results in either a mixed selenosulfide bond or disulfide bond (depending on the use of Sec or Cys), which can subsequently be reduced by thiolysis. A major disadvantage of thiolysis is that excess thiol must be used to drive the reaction to completion and then removed before using the Cys‐containing or Sec‐containing peptide in further applications. Here, we report a further advancement of this method as we have found that ascorbate at pH 4.5 and 25 °C will reduce the selenosulfide to the selenol. Ascorbolysis of the mixed disulfide between Cys and 5‐Npys is much less efficient but can be accomplished at higher concentrations of ascorbate at pH 7 and 37 °C with extended reaction times. We envision that our improved method will allow for in situ reactions with alkylating agents and electrophiles without the need for further purification, as well as a number of other applications. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
3.
There are many examples of bioactive, disulfide‐rich peptides and proteins whose biological activity relies on proper disulfide connectivity. Regioselective disulfide bond formation is a strategy for the synthesis of these bioactive peptides, but many of these methods suffer from a lack of orthogonality between pairs of protected cysteine (Cys) residues, efficiency, and high yields. Here, we show the utilization of 2,2′‐dipyridyl diselenide (PySeSePy) as a chemical tool for the removal of Cys‐protecting groups and regioselective formation of disulfide bonds in peptides. We found that peptides containing either Cys(Mob) or Cys(Acm) groups treated with PySeSePy in trifluoroacetic acid (TFA) (with or without triisopropylsilane (TIS) were converted to Cys‐S–SePy adducts at 37 °C and various incubation times. This novel Cys‐S–SePy adduct is able to be chemoselectively reduced by five‐fold excess ascorbate at pH 4.5, a condition that should spare already installed peptide disulfide bonds from reduction. This chemoselective reduction by ascorbate will undoubtedly find utility in numerous biotechnological applications. We applied our new chemistry to the iodine‐free synthesis of the human intestinal hormone guanylin, which contains two disulfide bonds. While we originally envisioned using ascorbate to chemoselectively reduce one of the formed Cys‐S–SePy adducts to catalyze disulfide bond formation, we found that when pairs of Cys(Acm) residues were treated with PySeSePy in TFA, the second disulfide bond formed spontaneously. Spontaneous formation of the second disulfide is most likely driven by the formation of the thermodynamically favored diselenide (PySeSePy) from the two Cys‐S–SePy adducts. Thus, we have developed a one‐pot method for concomitant deprotection and disulfide bond formation of Cys(Acm) pairs in the presence of an existing disulfide bond. 相似文献
4.
Delivering biomolecules, such as antibodies, proteins, and peptides, to the cytosol is an important and challenging aspect of drug development and chemical biology. Polyarginine—a well‐known cell‐penetrating peptide (CPP)—is capable of exploiting its positive charge and guanidium groups to carry a fused cargo into the cytosol. However, the precise mechanism by which this occurs remains ambiguous. In the present study, we established a new method of quantitatively assessing cell penetration. The method involves inducing cell death by using a polyarginine (R8) to deliver a peptide—ie, mitochondrial targeting domain (MTD)—to the cytosol. We found that 4,4′‐diisothiocyanatostilbene‐2,2′‐di‐sulfonate (DIDS)—an anion channel blocker—inhibited the ability of octa‐arginine (R8)–fused MTD to penetrate cells. Other anion channel blockers did not inhibit the penetration of peptides fused with R8. Comparison of DIDS with other structurally similar chemicals revealed that the isothiocyanate group of DIDS may be primarily responsible for the inhibitory effect than its stilbene di‐sulfonate backbone. These results imply that the inhibitory effect of DIDS may not be derived from the interaction between stilbene di‐sulfonate and the anion channels, but from the interaction between the isothiocyanate groups and the cell membrane. Our new MTD method enables the quantitative assessment of cell penetration. Moreover, further studies on the inhibition of CPPs by DIDS may help clarify the mechanism by which penetration occurs and facilitate the design of new penetrative biomolecules. 相似文献
5.
As a first step towards a viable prodrug strategy for short oligoribonucleotides, such as 2–5A and its congeners, adenylyl‐2′,5′‐adenosines bearing a 3‐(acetyloxy)‐2,2‐bis(ethoxycarbonyl)propyl group at the phosphate moiety, and an (acetyloxy)methyl‐ or a (pivaloyloxy)methyl‐protected 3′‐OH group of the 2′‐linked nucleoside have been prepared. The enzyme‐triggered removal of these protecting groups by hog liver carboxyesterase at pH 7.5 and 37° has been studied. The (acetyloxy)methyl group turned out to be too labile for the 3′‐ O‐protection, being removed faster than the phosphate‐protecting group, which results in 2′,5′‐ to 3′,5′‐isomerization of the internucleosidic phosphoester linkage. In addition, the starting material was unexpectedly converted to the 5′‐ O‐acetylated derivative. (Pivaloyloxy)methyl group appears more appropriate for the purpose. The fully deprotected 2′,5′‐ApA was accumulated as a main product, although, even in this case, the isomerization of the starting material takes place. 相似文献
6.
Protected dinucleoside‐2′,5′‐monophosphate has been prepared to develop a prodrug strategy for 2‐5A. The removal of enzymatically and thermally labile 4‐(acetylthio)‐2‐(ethoxycarbonyl)‐3‐oxo‐2‐methylbutyl phosphate protecting group and enzymatically labile 3′‐ O‐pivaloyloxymethyl group was followed at pH 7.5 and 37 °C by HPLC from the fully protected dimeric adenosine‐2′,5′‐monophosphate 1 used as a model compound for 2‐5A. The desired unprotected 2′,3′‐ O‐isopropylideneadenosine‐2′,5′‐monophosphate ( 9 ) was observed to accumulate as a major product. Neither the competitive isomerization of 2′,5′‐ to a 3′,5′‐linkage nor the P–O5′ bond cleavage was detected. The phosphate protecting group was removed faster than the 3′‐ O‐protection and, hence, the attack of the neighbouring 3′‐OH on phosphotriester moiety did not take place. 相似文献
7.
The modes of binding of 5′‐[4‐(aminoiminomethyl)phenyl]‐[2,2′‐Bifuran]‐5‐carboximidamide (DB832) to multi‐stranded DNAs: human telomere quadruplex, monomolecular R‐triplex, pyr/pur/pyr triplex consisting of 12 T*(T·A) triplets, and DNA double helical hairpin were studied. The optical adsorption of the ligand was used for monitoring the binding and for determination of the association constants and the numbers of binding sites. CD spectra of DB832 complexes with the oligonucleotides and the data on the energy transfer from DNA bases to the bound DB832 assisted in elucidating the binding modes. The affinity of DB832 to the studied multi‐stranded DNAs was found to be greater ( Kass ≈ 10 7M?1) than to the duplex DNA ( Kass ≈ 2 × 10 5M?1). A considerable stabilizing effect of DB832 binding on R‐triplex conformation was detected. The nature of the ligand tight binding differed for the studied multi‐stranded DNA depending on their specific conformational features: recombination‐type R‐triplex demonstrated the highest affinity for DB832 groove binding, while pyr/pur/pyr TTA triplex favored DB832 intercalation at the end stacking contacts and the human telomere quadruplex d[AG 3(T 2AG 3) 3] accommodated the ligand in a capping mode. Additionally, the pyr/pur/pyr TTA triplex and d[AG 3(T 2AG 3) 3] quadruplex bound DB832 into their grooves, though with a markedly lesser affinity. DB832 may be useful for discrimination of the multi‐sranded DNA conformations and for R‐triplex stabilization. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 8–20, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com 相似文献
8.
The unique ligands of [Ru(bipy) 2(bpda)](PF 6) 2 (1, BPDA=1,1′-biphenyl-2,2′-diamine) and [Ru(bipy) 2(dabipy)](PF 6) 2 (2, DABIPY=3,3′-diamino-2,2′-bipyridine) are atropisomeric (exhibit hindered rotation about the sigma bonds that connect the two aromatic groups), so the complexes are diasteromeric with conformation isomers possible for the atropisomeric ligands and configurational isomers possible at the metal centers. Only one diastereomer is observed in the solid-state in both cases. The seven- (1) and five-membered (2) chelate ring of dabipy and bpda (the ligand is bound through its pyridyl groups) ligands are δ when the configuration at the metal is Δ. No evidence for atropisomerization is found in solution. For 1, we conclude bpda binds stereospecifically; however, the atropisomerization barrier of dabipy may be sufficiently low for 2 to preclude the observation of diastereomers by low-temperature NMR spectroscopy. 相似文献
9.
The title compounds show a pronounced cation-directed ability to self-assemble in water and to gives columnar structures similar to four-stranded helices; for compound (5′→5′)-d(GpG), this leads to the formation of cholesteric and hexagonal liquid crystalline phases. Both phases are columnar and the cholesteric phase is left-handed. This behaviour is a further confirmation of the tendency of guanine derivatives to self-assemble to give stacked columnar structures whenever not impossible for structural reasons. The CD spectra of the aggregates in isotropic solutions are dominated by a negative exciton couplet centred around 250 nm associated to a left-handed columnar chirality. The shapes of the profiles, in the 220–300-nm region, for (5′→5′)-d(GpG) (in water or in saline solutions) and for (3′→3′)-d(GpG) (in KCl solution) are quasi-mirror images of those of poly(G) and (3′→5′)-d(GpG). The appearance of relatively intense CD signals around 280–300 nm in solution of (3′→3′)-d(GpG) in the presence of NaCl resembles that of (3′→5′)-d(GpG) in the presence of Rb + or Na +. In the compounds investigated in this work, which present two equivalent ends, one observes the two CD features that have been associated, in the current literature, with the signature of four-stranded parallel and antiparallel structures: hence the origin of these CD bands cannot be found in the polarity of the strands. Self-assembly is favoured by the addition of extra salt and the stabilising effect of K + is greater than that of Na +, in the case of (3′→3′)-d(GpG), an assembled species could be detected by CD only in the presence of extra salt. Chirality 10:734–741, 1998. © 1998 Wiley-Liss, Inc. 相似文献
10.
Quenching effects of bergenin, based on the electrochemiluminescence (ECL) of the tris(2,2′‐bipyridyl)‐ruthenium(II) (Ru(bpy) 32+)/tri‐n‐propylamine (TPrA) system in aqueous solution, is been described. The quenching behavior can be observed with a 100‐fold excess of bergenin over Ru(bpy) 32+. In the presence of 0.1 m TPrA, the Stern–Volmer constant ( KSV) of the ECL quenching is as high as 1.16 × 10 4 M ?1 for bergenin. The logarithmic plot of the inhibited ECL versus logarithmic plot of the concentration of bergenin was linear over the range 3.0 × 10 ?6–1.0 × 10 ?4 mol/L. The corresponding limit of detection was 6.0 × 10 ?7 mol/L for bergenin (S/N = 3). In the mechanism of quenching it is believed that the competition of the active free radicals between Ru(bpy) 32+/TPrA and bergenin was the key factor for the ECL inhibition of the system. Photoluminescence, cyclic voltammetry, coupled with bulk electrolysis, supports the supposition mechanism of the Ru(bpy) 32+/TPrA–bergenin system. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
11.
Fully protected pA2′p5′A2′p5′A trimers 1a and 1b have been prepared as prodrug candidates for a short 2′‐5′ oligoadenylate, 2‐5A, and its 3′‐ O‐Me analog, respectively. The kinetics of hog liver carboxyesterase (HLE)‐triggered deprotection in HEPES buffer (pH 7.5) at 37° has been studied. The deprotection of 1a turned out to be very slow, and 2‐5A never appeared in a fully deprotected form. By contrast, a considerable proportion of 1b was converted to the desired 2‐5A trimer, although partial removal of the 3′‐ O‐[(acetyloxy)methyl] group prior to exposure of the adjacent phosphodiester linkage resulted in 2′,5′→3′,5′ phosphate migration and release of adenosine as side reactions. 相似文献
12.
Recent studies have shown that a loss of methylthioadenosine phosphorylase ( MTAP) gene expression exerts a tumor‐promoting effect, including induction of invasiveness, enhanced cell proliferation, and resistance against cytokines. To date, the molecular mechanisms underlying these effects remain unknown. Since the loss of MTAP expression resulted in induced secretion of 5′‐deoxy‐5′‐(methylthio)adenosine (MTA), we hypothesized that MTA might modulate the observed effects. We first determined MTA levels produced by tumor cells in vitro and in situ by means of stable isotope dilution liquid chromatography tandem mass spectrometry. Subsequently, we revealed induction of matrix metalloproteinase (MMP) and growth factor gene expression in melanoma cells accompanied by enhanced invasion and vasculogenic mimicry. In addition, MTA induced the secretion of basis fibroblast growth factor (bFGF) and MMP3 from fibroblasts and the upregulation of activator protein‐1 (AP‐1) activity in melanoma cells and fibroblasts. In summary, we demonstrated a tumor‐supporting role of MTA. J. Cell. Biochem. 106: 210–219, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
13.
It was found that meloxicam could enhance the chemiluminescence (CL) of the tris(2,2'‐bipyridine) ruthenium(II)–Ce(IV) system in the medium of sulfate acid. Based on this phenomenon a new flow‐injection system with chemiluminescent detection has been proposed for determination of meloxicam. Under optimum conditions, meloxicam had a good linear relationship with the CL intensity in the concentration range of 6.0 10 ?4 to 1.0 µg/mL and the detection limit was 3.7 × 10 ?4 µg/mL. The proposed method was applied to detect meloxicam in tablets and a satisfactory recovery was obtained. The possible mechanism for this CL system is also discussed in this paper. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
Electrochemiluminescence (ECL) of tris(2,2’‐bipyridyl)ruthenium(II) [Ru(bpy) 32+] is an active research area and includes the synthesis of ECL‐active materials, mechanistic studies and broad applications. Extensive research has been focused on this area, due to its scientific and practical importance. In this mini‐review we focus on the bio‐related applications of ECL. After a brief introduction to Ru(bpy) 32+ ECL and its mechanisms, its application in constructing an effective bioassay is discussed in detail. Three types of ECL assay are covered: DNA, immunoassay and functional nucleic acid sensors. Finally, future directions for these assays are discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
15.
Function studies of many proteins are waited to develop after genome sequencing. High‐throughout technology of gene cloning will strongly promote proteins' function studies. Here we describe a ligation‐independent cloning (LIC) method, which is based on the amplification of target gene and linear vector by PCR using phosphorothioate‐modified primers and the digestion of PCR products by λ exonuclease. The phosphorothioate inhibits the digestion and results in the generation of 3′ overhangs, which are designed to form complementary double‐stranded DNA between target gene and linear vector. We compared our phosphorothioate primer cloning methods with several LIC methods, including dU primer cloning, hybridization cloning, T4 DNA polymerase cloning, and in vivo recombination cloning. The cloning efficiency of these LIC methods are as follows: phosphorothioate primer cloning > dU primer cloning > hybridization cloning > T4 DNA polymerase cloning >> in vivo recombination cloning. Our result shows that the 3′ overhangs is a better cohesive end for LIC than 5′ overhang and the existence of 5′phosphate promotes DNA repair in Escherichia coli, resulting in the improvement of cloning efficiency of LIC. We succeeded in constructing 156 expression plasmids of Aeropyrum pernix genes within a week using our method. 相似文献
16.
UV absorption data analysis has been used to evaluate equilibrium constants of the pH‐induced interaction of 2,2′‐Bipy with polyadenylnic‐polyuridylic acid in aqueous solution. The conditional probabilities hard model has been adopted in treatment of concentration diagrams calculated by the soft modelling‐based Multivariate Curve Resolution‐Alternating Least Squares approach. Intrinsic binding constant (lgK g = 1.93), and the cooperativity parameter (ω = 340), were calculated as the best fit. The plot of the experimental binding constant versus 2,2′‐Bipy equilibrium concentration shows two modes of ligand with polymer interactions. The equilibrium hard model correctly reproduced the binding constant variations observed in the experiment. The results indicated that ligand binding in two steps is governed by a cooperative process, that is, the enhancement of deprotonated structure stability. It would appear that proposed calculation approach can be used in future combined hard modelling theoretical and soft modelling experimental works. © 2013 Wiley Periodicals, Inc. Biopolymers 99:621–627, 2013. 相似文献
17.
Non-enzymatic reactions of the 3,4-oxide of 2,2′,5,5′-tetrachlorobiphenyl (TCB) with methionine or N-acetylmethionine in ethanol/neutral buffer at 37°C proceeded very slowly to yield an approx. 1 : 1 ratio of 3- and 4-methylthio-TCB. Under similar conditions reaction of TCB 3,4-oxide with cysteine proceeded about 100 times more rapidly to yield an approx. 1 : 1 ratio of 3- and 4-(cystein- S-yl)-TCB as the major products. Cystein- S-yl-3,4-dihydro-hydroxy-TCB(s) was also formed as a minor product from reaction of TCB 3,4-oxide with cysteine in dimethyl sulfoxide/neutral buffer. TCB 3,4-oxide did not react detectably with glutathione in ethanol/neutral buffer at 37°C or 70°C, but reaction in ethanol/pH 8.7 buffer at 37°C proceeded very rapidly to yield about a 1 : 1 ratio of 3- and 4-(glutathion- S-yl)-TCB and of two glutathion- S-yl-TCB precursors. Glutathion- S-yl-TCB(s) and its precursor(s) were also formed rapidly in a rat liver cytosol-catalyzed reaction of TCB 3,4-oxide with glutathione at neutral pH. The glutathion- S-yl-TCBs readily degraded upon concentration in aqueous alcohol solutions under mild conditions to yield compounds tentatively identified as [ N-(5-carboxy-1-pyrrolin-2-yl)-1-glycinocystein- S-yl]-TCBs, (1-glycinocystein- S-yl)-TCBs and 2-oxopyrrolidine-5-carboxylic acid. Rats given a single dose of TCB excreted about 0.07% of the dose in the feces during the first 4 days as 3-methylthio-TCB, 4-methylthio-TCB, 4-methylsulfonyl-TCB, methylthio-hydroxy-TCBs (tentatively identified) and mercapto-TCB(s) (tentatively identified) in about a 1 : 5 : 0.1 : 0.1 : 0.05 ratio, respectively. Rats given an equimolar dose of TCB 3,4-oxide excreted similar ratios of these fecal metabolites in approx. 10-fold greater quantities. Mice given TCB excreted about 0.1% of the dose in the feces during the first 4 days as 3-methylthio-TCB, 4-methylthio-TCB and 3-methylsulfonyl-TCB in about a 1.5 : 1 : 0.05 ratio, respectively. Methylthio-TCBs were not detected (<0.0004% of the dose) in the bile of a cannulated rat given a single dose of TCB. About 1.5% of the TCB dose was excreted in the bile as glutathion-S-yl-TCB(s) and its precursor(s). Collectively, the data indicate that TCB 3,4-oxide is a primary metabolic intermediate in the formation of methylthio-metabolites of TCB. 相似文献
19.
Protein synthesis is often regulated at the level of initiation of translation, making it a critical step. This regulation occurs by both the cis‐regulatory elements, which are located in the 5′‐ and 3′‐UTRs (untranslated regions), and trans‐acting factors. A breakdown in this regulation machinery can perturb cellular metabolism, leading to various physiological abnormalities. The highly structured UTRs, along with features such as GC‐richness, upstream open reading frames and internal ribosome entry sites, significantly influence the rate of translation of mRNAs. In this review, we discuss how changes in the cis‐regulatory sequences of the UTRs, for example, point mutations and truncations, influence expression of specific genes at the level of translation. Such modifications may tilt the physiological balance from healthy to diseased states, resulting in conditions such as hereditary thrombocythaemia, breast cancer, fragile X syndrome, bipolar affective disorder and Alzheimer's disease. This information tends to establish the crucial role of UTRs, perhaps as much as that of coding sequences, in health and disease. 相似文献
20.
Bioactive, volatile, secondary and tertiary fragrance alcohols are efficiently released by intramolecular neighboring‐group‐assisted hydrolysis of 2,2′‐bis(carbamoyl)dibenzoates at neutral pH. The stepwise cyclization of 2,2′‐[(methylimino)bis(propane‐3,1‐diylcarbamoyl)]dibenzoates is followed by the re‐opening of the intermediately formed diphthalimide and proceeds in an overall four‐step consecutive reaction sequence. Kinetic rate constants for all four reaction steps could be determined pairwise by reversed‐phase HPLC. At neutral pH, secondary alcohols were released by one order of magnitude faster than the tertiary alcohols, and the rate constants for the re‐opening of the diphthalimides were found to be in the same order of magnitude as the release of the tertiary alcohols. Dynamic headspace analysis on a dry cotton surface finally confirmed the efficient release of tertiary alcohols under mild reaction conditions generally encountered for applications in functional perfumery. 相似文献
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