Bioinspired Stable and Photoluminescent Assemblies for Power Generation

Peptide assemblies are ideal components for eco‐friendly optoelectronic energy harvesting devices due to their intrinsic biocompatibility, ease of fabrication, and flexible functionalization. However, to date, their practical applications have been limited due to the difficulty in obtaining stable, high‐performance devices. Here, it is shown that the tryptophan‐based simplest peptide cyclo‐glycine‐tryptophan (cyclo‐GW) forms mechanically robust (elastic modulus up to 24.0 GPa) and thermally stable up to 370 °C monoclinic crystals, due to a supramolecular packing combining dense parallel β‐sheet hydrogen bonding and herringbone edge‐to‐face aromatic interactions. The directional and extensive driving forces further confer unique optical properties, including aggregation‐induced blue emission and unusual stable photoluminescence. Moreover, the crystals produce a high and sustained open‐circuit voltage (1.2 V) due to a high piezoelectric coefficient of 14.1 pC N^?1. These findings demonstrate the feasibility of utilizing self‐assembling peptides for fabrication of biointegrated microdevices that combine high structural stability, tailored optoelectronics, and significant energy harvesting properties.     

2,5-diketopiperazines in food and beverages: Taste and bioactivity

2,5-Diketopiperazines (2,5-DKPs) have been found to occur in a wide range of food and beverages, and display an array of chemesthetic effects (bitter, astringent, metallic, and umami) that can contribute to the taste of a variety of foods. These smallest cyclic peptides also occur as natural products and have been found to display a variety of bioactivities from antibacterial, antifungal, to anthroprotective effects and have the potential to be used in the development of new functional foods. An overview of the synthesis of these small chiral molecules and their molecular properties is presented. The occurrence, taste, and bioactivity of all simple naturally occurring 2,5-DKPs to date have been reviewed and those found in food from yeasts, fungi, and bacteria that have been used in food preparation or contamination, as well as metabolites of sweeteners and antibiotics added to food are also reviewed.     

环（组氨酸-脯氨酸）二肽的高温高压辅助合成工艺优化

将高温高压技术应用于环（组氨酸-脯氨酸）二肽（cyclo(His-Pro),CHP）的制备。以二肽甲酯盐酸盐为原料,采用高温高压辅助环化法在水中制备CHP,通过单因素试验考察了各种反应变量如压力、时间、溶液pH值以及底物质量浓度对CHP产率的影响,采用正交试验对高温高压辅助环化工艺条件进行优化。采用超高效液相色谱法和电喷雾质谱技术对产物中的CHP进行定量和定性分析。结果表明,最佳的反应条件为：反应压力0.20 MPa、反应时间3.5 h、溶液pH 6.0、底物质量浓度15 mg/mL。在此条件下可以得到较高产率（91.35%）的CHP,并且反应中没有观察到消旋。与传统的甲醇回流法相比,本研究的环化方法省时、高效、环保,并且能够得到较高的产率,同时产物没有发生消旋。     

Geranylation of Cyclic Dipeptides by the Dimethylallyl Transferase AnaPT Resulting in a Shift of Prenylation Position on the Indole Ring

The dimethylallyl transferase AnaPT from Neosartorya fischeri is involved in the biosynthesis of acetylaszonalenin and catalyses the regioselective and stereospecific C3α‐prenylation of (R)‐benzodiazepinedione in the presence of dimethylallyl diphosphate. This enzyme also converts several tryptophan‐containing cyclic dipeptides to C3α‐prenylated indolines. In this study, we demonstrate the geranylation of (R)‐benzodiazepinedione and five other cyclic dipeptides by AnaPT in the presence of geranyl diphosphate (GPP). Interestingly, structure elucidation by NMR and MS analyses revealed that, with GPP, the geranyl moiety is attached to C‐6 or C‐7 rather than C‐3 of the indole ring of the enzyme products. For (R)‐benzodiazepinedione, one dominant C6‐geranylated derivative was obtained, whereas the other five substrates yielded both C6‐ and C7‐geranylated products. Neither acceptance of GPP by a dimethylallyl transferase from the dimethylallyltryptophan synthase superfamily, nor the alkylation shift from C‐3 to the benzene ring of the indole nucleus has been reported previously.     

Antibacterial and Antibiofilm Properties of Self-Assembled Dipeptide Nanotubes

Over recent decades, multidrug-resistant pathogens have become a global concern, with WHO even considering it one of the biggest threats to global health, food security, and development today, which led to the search for alternative antibacterial agents. A special class is formed by peptides composed by the diphenylalanine motif whose antibacterial properties result from their supramolecular arrangement into nanotubes. However, several other dipeptides that also form nanotubes have been largely overlooked. Here, we present the antibacterial activity of four dipeptide nanotubes. The results point to diverse mechanisms through which dipeptide nanotubes exert their effect against bacteria. Antibacterial activity was similar for dipeptide nanotubes sufficiently wide to allow water flux while dipeptides displaying smaller channels were inactive. This suggests that two of the tested dipeptides, L-Phe-L-Phe (FF, diphenylalanine) and L-Leu-L-Ser (LS), are pore forming structures able to induce membrane permeation and affect cellular hydration and integrity. Of these two dipeptides, only FF demonstrated potential to inhibit biofilm formation. The amyloid-like nature and hydrophobicity of diphenylalanine assemblies are probably responsible for their adhesion to cell surfaces preventing biofilm formation and bacteria attachment.     

含酪氨酸残基的食源性ACE抑制二肽的稳定性研究

本文以含酪氨酸残基的食源性血管紧张素转化酶(Angiotensin Converting Enzyme,ACE)抑制二肽为研究对象,以食源性寡肽的保存率和ACE抑制活性为指标,通过反相高效液相色谱检测二肽的热稳定性和抗胃肠道消化能力。结果表明在37、50、70℃条件下,食源性二肽Ile-Tyr(IY)、Leu-Tyr(LY)、Ala-Tyr(AY)和Ser-Tyr(SY)均有较好的热稳定性。在100℃下,SY相对IY、LY和AY热稳定性略低,其中IY表现出最好的热稳定性。AY、IY、LY和SY均具有较好的抗胃蛋白酶和胰蛋白酶消化吸收能力,经人工胃液反应2 h后,肽保存率均高于90%;经人工肠液反应6 h,肽保存率范围在83.99%~87.27%。本研究为进一步研究食源性二肽稳定性提供了重要的理论依据。     

Lipopeptidic surfactants. II. Acidic and basic Nα-lauroyl-L-arginine dipeptides from pure amino acids

In this paper, the second part of a systematic study whose aim deals with the influence of the terminal amino acid side chain on the properties of Nα-lauroyl arginyl dipeptides is reported. Nα-lauroyl arginyl dipeptides that contain an acidic amino acid (glutamic acid) or a basic amino acid (lysine) as terminal amino acid have been prepared by peptide synthesis methods. These compounds have been synthesized as methyl esters (cationic surfactants) and free α-carboxylic acids (amphoteric surfactants), and their fundamental surfactant properties and antimicrobial activity have been evaluated. The properties of these compounds have been compared to the properties of the cationic monomer derivative methyl ester of Nα-lauroyl arginine and of the amphoteric monomer derivative Nα-lauroyl arginine reported earlier. The compounds are soluble in water and show surface activity, although in the case of the amphoteric Nα-lauroyl arginyl dipeptide containing glutamic acid these two properties depend on the solution pH. The cationic Nα-lauroyl arginyl dipeptides are antimicrobial agents. However, only the amphoteric compound containing lysine may be considered antimicrobial.     

The tRNA-Dependent Biosynthesis of Modified Cyclic Dipeptides

In recent years it has become apparent that aminoacyl-tRNAs are not only crucial components involved in protein biosynthesis, but are also used as substrates and amino acid donors in a variety of other important cellular processes, ranging from bacterial cell wall biosynthesis and lipid modification to protein turnover and secondary metabolite assembly. In this review, we focus on tRNA-dependent biosynthetic pathways that generate modified cyclic dipeptides (CDPs). The essential peptide bond-forming catalysts responsible for the initial generation of a CDP-scaffold are referred to as cyclodipeptide synthases (CDPSs) and use loaded tRNAs as their substrates. After initially discussing the phylogenetic distribution and organization of CDPS gene clusters, we will focus on structural and catalytic properties of CDPSs before turning to two recently characterized CDPS-dependent pathways that assemble modified CDPs. Finally, possible applications of CDPSs in the rational design of structural diversity using combinatorial biosynthesis will be discussed before concluding with a short outlook.     

FgaPT2酶催化合成C-4异戊烯基化吲哚二酮哌嗪和定向诱变增强收率

在二甲基烯丙基二磷酸存在下,通过FgaPT2的酶催化合成C-4异戊烯化吲哚二酮哌嗪,对合成的产物进行了抗肿瘤、抗细菌、抗真菌、抗氧化活性测试,对生物活性最高的产物,研究了通过定点诱变提高酶合成产率的可行性。结果表明,FgaPT2酶催化合成了7个C4-异戊烯化吲哚二酮哌嗪,FgaPT2对底物具有一定的选择性,C4-异戊二烯化显著提高吲哚二酮哌嗪的生物活性,尤其是异戊二烯化产物 6b。Arg244的定点诱变表明,52.6%的FgaPT2突变体,提高了6b的合成产率,动力学参数验证了6a与突变FgaPT2之间的相互作用,可以提高异戊二烯基的合成产率。