新型耐腐蚀含氟环氧乙烯基酯树脂的合成与性能

以含氟环氧树脂（F-EP）、丙烯酸（AA）和甲基丙烯酸（MAA）为单体,用顺丁烯二酸（MA）进行改性,合成了含氟环氧乙烯基酯树脂（F-EVER）。用傅里叶红外光谱、热重分析、力学性能分析等手段对产物进行表征,研究了树脂的耐腐蚀性能。结果表明：当以N,N-二甲基甲酰胺（DMF）为催化剂,羧基与环氧基摩尔比为0.9,MA与...     

Efficient adsorption and desorption of Cu2+ by a novel acid-resistant magnetic weak acid resin

A novel magnetic weak acid resin NDMC-1 was prepared in the presence of methyl acrylate（MA）,divinylbenzene（DVB） and titanate coupling agent（TCA） coated 7-Fe₂O₃ particles.To evaluate the adsorption of Cu²⁺ on the obtained resin NDMC-1,another two magnetic resins NDMC-0（the precursor of NDMC-1 without hydrolyzation） and NDMO-l（the synthesized weak acid resin using oleic acid coatedγ-Fe₂O₃） were chosen for comparison.The results showed that the carboxyl groups were formed after hydrolyzation,and NDMC-1 exhibited a greater adsorption capacity to Cu²⁺.The desorption experiment demonstrated that the desorption ratio at pH 2（95.14%） was greatly higher than pH 3（25.97%）.Moreover,the magnetic resin NDMC-1 was proved to be stable at pH 2,extending the application of magnetic materials which were always considered to be acid-nonresistant.     

Synthesis of Hydroxymethyl Side-Chained α-Aminoxy Diamide

Unnatural polar α-aminoxy acid residue with proteingenous hydroxymethyl side chain, a building block of the peptidomimetic foldamer of α-aminoxy peptide, was synthesized starting from natural amino acid L-serine. The starting material, L-serine, undergoes a reaction sequence to produce compound 1 in three steps: (1) the neighboring carboxyl group participates in diazotization/bromination to transform the amino group to a bromo group, (2) the C-terminal carboxyl group is protected, and (3) bromide is S_N2-displaced by N-hydroxyl phthalimide to introduce a N?O bond. After several conventional deprotection/coupling reactions, compound 1 is easily transformed to an α-aminoxy diamide, which can be widely used in peptidomimetics design.     

Deprotection of the S-trimethylacetamidomethyl (Tacm) group using silver tetrafluoroborate: application to the synthesis of porcine brain natriuretic peptide-32 (pBNP-32)

Silver tetrafluoroborate (AgBF4) in trifluoroacetic acid (TFA) has been found to cleave the S-trimethyl-acetamidomethyl (Tacm) group or the S-acetamidomethyl (Acm) group without affecting other functional groups in a peptide chain. A newly isolated porcine brain natriuretic peptide-32 (pBNP-32) was synthesized by the combined use of the S-Tacm group and AgBF4 deprotection. The synthetic pBNP-32 was obtained in better yield by the AgBF4 procedure than by the standard I2 procedure. The synthetic pBNP-32 has the highest chick rectum relaxant activity among the known members of the atrial natriuretic peptide-brain natriuretic peptide (ANP-BNP) families. Somatostatin was also synthesized by the Fmoc-based solid-phase method using S-Tacm and AgBF4. In this synthesis, the recently developed reagent tetrafluoroboric acid (HBF4) was applied to cleave the peptide from the resin.     

pH‐sensitive hemolysis by random copolymers of alkyl acrylates and acrylic acid

We have been designing and synthesizing synthetic polymers that mimic viral fusogenic peptides, which contain peptide residues having alkyl groups and carboxyl groups. We have synthesized two different types of such polymers, and their abilities to hemolyse red blood cells at pH 7.4 and 5.5 are compared here. The polymers are poly(2‐alkylacrylic acid)s such as poly(2‐propylacrylic acid), and random copolymers of poly(alkyl acrylate‐co‐acrylic acid) where the alkyl group is propyl or butyl. We have found that the poly(2‐alkylacrylic acid)s such as poly(2‐propylacrylic acid) are significantly more hemolytic at acidic pH than the random copolymers of equivalent propyl and carboxyl contents.     

酶促合成肽的研究 II: 含羧基侧链氨基酸的肽的酶促合成

用嗜热菌酶酶促合成了一系列含门冬氨酸、谷氨酸的肽. 实验证明, 缩合反应中羧基组份中的门冬氨酸β-羧基或谷氨酸γ-羧基毋需保护. 同时也研究了邻近氨基酸残基对缩合反应的影响.     

Synthesis and purification of aggregation-prone hydrophobic peptides by the incorporation of an Fmoc dipeptide with the peptide bond protected with a modified 2-hydroxy-4-methoxybenzyl (Hmb) group

The dipeptide Fmoc-Val-(2-hydroxy-4-methoxybenzyl)Gly-OBzl was synthesized and the 2-hydroxyl group carbamoylated to give a Boc-N(CH₃)CH₂CH₂N(CH₃)CO–, (Boc-Nmec-) modification of the 2-hydroxy-4-methoxybenzyl (Hmb) group. After catalytic hydrogenation and purification, the resulting dipeptide Fmoc-Val-(Boc-Nmec-Hmb)Gly-OH was used in solid phase peptide synthesis. During treatment with TFA, the peptide was released from the resin and the Boc group cleaved. The peptide could then be purified with an alkylated peptide bond carrying a cationic charge that both increased the solubility of the peptide during the purification steps and facilitated analysis by MALDI-TOF mass spectrometry. The Nmec group was cleaved by intramolecular cyclization under slightly alkaline conditions, followed by cleavage of the Hmb group by TFA to give the fully deprotected peptide.     

The oxazole-triamide rearrangement. Application to peptide synthesis

The carboxyl group of a N-acylated amino acid may be protected by conversion to an oxazole derivative which, on photoxygenation, regenerates the carboxyl group in activated (triamide) form for peptide synthesis.     

一种低分子量带有羧基的聚丙烯酸酯丙烯酸树脂的制备和性质

制备了一种紫外光固化预聚物——带有羧基的低分子量聚丙烯酸酯丙烯酸树脂(Polyacrylate acrylic resin, PAAR).其主链由丙烯酸烷基酯和丙烯酸进行共聚而得,当采用丙烯酸甲酯、丙烯酸乙酯和丙烯酸(摩尔比1:1:1)作为共聚单体,引发剂AIBN为1.5%,链转移剂十二硫醇为2.5%时,聚合得到的聚丙烯酸酯(Polyacrylate, PA)分子量在1100-1400之间,多分散性小于2,反应速率快,转化率高;由这种PA和甲基丙烯酸缩水甘油酯(GMA)进行酯化反应,制备得到最终产物聚丙烯酸酯丙烯酸树脂,酯化率可以达到80%以上,其光固化膜具有较好的涂膜硬度和柔韧性,光泽度饱满.     

爱滋病病毒中肽段的酶促合成

为了进一步研究酶促合成在多肽合成中的实际应用,选择合成了爱滋病病毒(人类免疫缺损病毒,HIV-I)的gp41中氨基酸序列598-609的三个肽段,该部分是HIV-I中的2个抗原决定簇部分,H-Leu-Glg-Leu-Trp-Glg-cgs-Ser-Glg-Lgs-Leu-Ile-Cgs-OH可以作为抗原来检测HIV抗体.     

Histidine as the functional group for a chelating ion exchanger

In the chelating ion exchanger synthesized, the amino group of histidine is attached chemically via the azide method to the carboxyl group of Amberlite IRC-50. A flow system based on a spectrophotometric detector, with 4-(2-pyridylazo) resorcinol as reagent, is described for fast assays of eluted cations. The pH dependence of the metal extraction is reported for Ag(I), Au(III), Cu(II), Fe(III), Hg(II), Ni(II) and Zn(II) ions. The resin exhibits no affinity for the alkali or alkaline earth metals. The uptake of traces of the specified elements from synthetic samples by a short (90 mm) column of the histidine-containing resin was in the range 94–100% and the retained metals were readily eluted by means of 2 M hydrochloric or hydrobromic acid. In column operation, mercury was quantitatively recovered even in the presence of large excesses of various ligands. The recoveries of the trace metals were good at the usual pH of natural waters.     

Tetrafluoroboric acid, a useful deprotecting reagent in peptide synthesis

We have found that tetrafluoroboric acid (HBF4) in trifluoroacetic acid (TFA) in the presence of thioanisole cleaves various protecting groups currently used in peptide synthesis. HBF4 in TFA cleaves an amino acid amide from 4-methylbenzhydrylamine resin more effectively than trifluoromethanesulfonic acid in TFA. Lamprey gonadotropin-releasing hormone (a 10-residue peptide amide) was synthesized using 1 M HBF4-thioanisole in TFA by both solution-phase and solid-phase methods.     

Convergent solid phase peptide synthesis. v. synthesis of the 1-4, 32-34, and 53-59 protected segments of the toxin ii of androctonus australis hector.

Two protected peptide segments corresponding to the sequence 32-34 and 53-59 of toxin II of the north African scorpion Androctonus australis Hector have been synthesized on a photolabile Nbb-resin using the TFA-labile Boc -amino protection and HF-labile side chain protecting groups. A third protected peptide corresponding to segment 1-4 has been synthesized on the same resin but with a t-butyl group for β protection of aspartic acid and a Z group on the lysine side chain. For this last segment a combination of Boc and Fmoc groups for -amino protection has been used successfully on the Nbb-resin. After photolysis the crude peptides have been treated by solvent extraction and semi-preparative HPLC to yield highly purified segments. These syntheses show the flexibility of the convergent solid phase approach and how segments with different and independent protecting groups can be assembled by solid phase peptide procedure.     

A novel class of chemically modified iodo-containing resins: design, synthesis and application to mass spectrometry-based proteome analysis

A novel class of chemically modified iodo-containing resins with isotope-labeled tagging for mass spectrometry-based proteome analysis is described. This iodo-containing resin contains a thiol-reactive group that is used to capture the cysteine (Cys)-containing peptides from peptide mixtures, one 'tag' amino acid, and an aminomethyl polystyrene resin with Rink Amide Linker. The 'tag' amino acid is synthesized in both heavy and light isotope-coded forms and therefore permits the direct relative quantification of peptides/proteins through mass spectrometric analysis. In the iodo-containing resin strategy, the Cys-containing peptides of two samples covalently captured by either light or heavy iodo-containing resin were mixed and washed extensively under stringent conditions. Then the Cys-containing peptides were retrieved by acid-catalyzed elution. Finally, the eluted peptides were directly analyzed by micro liquid chromatography/mass spectrometry for identification and relative quantification. The iodo-containing resins were synthesized by a simple but effective method. Their abilities to identify and quantify the Cys-containing part in two samples were proved by the analysis of mixtures of amino acids, peptides and proteins.     

On the use of carboxamidomethyl esters (cam esters) in the synthesis of model peptides. scope and limitations

The usefulness of carboxamidomethyl esters (CAM esters) as a carboxyl protecting group for peptide synthesis was demonstrated. The synthesis of the chemotactic peptide For-Met-Leu-Phe-OH as well as the synthesis of Met-enkephalin using CAM ester as carboxyl terminal protection were performed. These esters showed good stability during acidolytic removal of BOC N-protecting group, during hydrogenolysis of Z N-protecting group and during removal of FMOC N-protecting group. CAM esters were selectively and rapidly cleaved by NaOH 0.5 N or by Na₂CO₃. However, we did not succeed in removing selectively the CAM ester when β-benzyl ester of aspartic acid was present in the sequence.     

Peptide‐Stabilized,Fluorescent Silver Nanoclusters: Solid‐Phase Synthesis and Screening

Few‐atom silver nanoclusters (AgNCs) can exhibit strong fluorescence; however, they require ligands to prevent aggregation into larger nanoparticles. Fluorescent AgNCs in biopolymer scaffolds have so far mainly been synthesized in solution, and peptides have only found limited use compared to DNA. Herein, we demonstrate how solid‐phase methods can increase throughput dramatically in peptide ligand screening and in initial evaluation of fluorescence intensity and chemical stability of peptide‐stabilized AgNCs (P‐AgNCs). 9‐Fluorenylmethyloxycarbonyl (Fmoc) solid‐phase peptide synthesis on a hydroxymethyl‐benzoic acid (HMBA) polyethylene glycol polyacrylamide copolymer (PEGA) resin enabled on‐resin screening and evaluation of a peptide library, leading to identification of novel peptide‐stabilized, fluorescent AgNCs. Using systematic amino acid substitutions, we synthesized and screened a 144‐member library. This allowed us to evaluate the effect of length, charge, and Cys content in peptides used as ligands for AgNC stabilization. The results of this study will enable future spectroscopic studies of these peptide‐stabilized AgNCs for bioimaging and other applications.     

Der 2-Trimethylsilyläthyl-Rest als selektiv abspaltbare Carboxy-Schutzgruppe

The 2-trimethylsilylethyl residue, a selectively cleavable carboxyl protecting group In a search for new carboxyl protecting groups suitable for use in peptide synthesis, 2-trimethylsilylethyl esters [-COOCH₂CH₂Si(CH₃)₃] of several N-protected amino acids have been prepared. These esters can be synthesized in good yields from N^a-benzyloxycarbonyl-amino acids and 2-trimethylsilylethanol with dicyclohexylcarbodiimide in the presence of pyridine. They are stable under a wide variety of conditions used during coupling and work-up in peptide synthesis. For removal the 2-trimethylsilylethyl group is readily cleaved by fluoride ions, preverably using a quaternary ammonium fluoride in dimethylformamide. Some side reactions which occurred during the removal of the 2-trimethylsilylethyl group are discussed. Special attention has been paid to the question of racemization during the treatment with fluoride ions. No. evidence of racemization was found in any of the cases examined.     

Synthesis of 2-(4,6-dimethoxy-1,3,5-triazin-2-yloxyimino) derivatives: application in solution peptide synthesis

A new class of 1,3,5-triazinyloxyimino derivatives were prepared, characterized and tested for reactivity in solution peptide synthesis. The new triazinyloxyimino derivatives failed to activate the carboxyl group during formation of peptide bonds, but gave the corresponding N-triazinyl amino acid derivatives as a major product. The oxyma (ethyl 2-cyano-2-(hydroxyimino)acetate) uronium salt was superior to other uronium salts in terms of racemization, while 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT, 9) gave the best results.     

Comparative investigation of the cleavage step in the synthesis of model peptide resins: implications for Nalpha-9-fluorenylmethyloxycarbonyl-solid phase peptide synthesis

Based on our studies of the stability of model peptide-resin linkage in acid media, we previously proposed a rule for resin selection and a final cleavage protocol applicable to the Nalpha-tert-butyloxycarbonyl (Boc)-peptide synthesis strategy. We found that incorrect choices resulted in decreases in the final synthesis yield, which is highly dependent on the peptide sequence, of as high as 30%. The present paper continues along this line of research but examines the Nalpha-9-fluorenylmethyloxycarbonyl (Fmoc)-synthesis strategy. The vasoactive peptide angiotensin II (AII, DRVYIHPF) and its [Gly8]-AII analogue were selected as model peptide resins. Variations in parameters such as the type of spacer group (linker) between the peptide backbone and the resin, as well as in the final acid cleavage protocol, were evaluated. The same methodology employed for the Boc strategy was used in order to establish rules for selection of the most appropriate linker-resin conjugate or of the peptide cleavage method, depending on the sequence to be assembled. The results obtained after treatment with four cleavage solutions and with four types of linker groups indicate that, irrespective of the circumstance, it is not possible to achieve complete removal of the peptide chains from the resin. Moreover, the Phe-attaching peptide at the C-terminal yielded far less cleavage (50-60%) than that observed with the Gly-bearing sequences at the same position (70-90%). Lastly, the fastest cleavage occurred with reagent K acid treatment and when the peptide was attached to the Wang resin.