Phosphino Amino Acids: Novel Water-Soluble Ligands for Coordination Chemistry of Transition Metals

An easy and effective access to water-soluble phospino amino acids by condensation of PH-containing phosphines with formaldehyde and amino acids is presented here.     

Inside Back Cover: Prolinyl Nucleotides Drive Enzyme-Free Genetic Copying of RNA (Angew. Chem. Int. Ed. 41/2023)

Proline is one of the proteinogenic amino acids. It is found in all kingdoms of life. It also has remarkable activity as an organocatalyst and is of structural importance in many folded polypeptides. Here, we show that prolinyl nucleotides with a phosphoramidate linkage are active building blocks in enzyme- and ribozyme-free copying of RNA in the presence of monosubstituted imidazoles as organocatalysts. Both dinucleotides and mononucleotides are incorporated at the terminus of RNA primers in aqueous buffer, as instructed by the template sequence, in up to eight consecutive extension steps. Our results show that condensation products of amino acids and ribonucleotides can act like nucleoside triphosphates in media devoid of enzymes or ribozymes. Prolinyl nucleotides are metastable building blocks, readily activated by catalysts, helping to explain why the combination of α-amino acids and nucleic acids was selected in molecular evolution.     

Amino Acid Modified RNA Bases as Building Blocks of an Early Earth RNA-Peptide World

Fossils of extinct species allow us to reconstruct the process of Darwinian evolution that led to the species diversity we see on Earth today. The origin of the first functional molecules able to undergo molecular evolution and thus eventually able to create life, are largely unknown. The most prominent idea in the field posits that biology was preceded by an era of molecular evolution, in which RNA molecules encoded information and catalysed their own replication. This RNA world concept stands against other hypotheses, that argue for example that life may have begun with catalytic peptides and primitive metabolic cycles. The question whether RNA or peptides were first is addressed by the RNA-peptide world concept, which postulates a parallel existence of both molecular species. A plausible experimental model of how such an RNA-peptide world may have looked like, however, is absent. Here we report the synthesis and physicochemical evaluation of amino acid containing adenosine bases, which are closely related to molecules that are found today in the anticodon stem-loop of tRNAs from all three kingdoms of life. We show that these adenosines lose their base pairing properties, which allow them to equip RNA with amino acids independent of the sequence context. As such we may consider them to be living molecular fossils of an extinct molecular RNA-peptide world.     

Analysis of Thermal Decomposition Patterns of Aromatic and Heteroaromatic Amino Acids

Abstract

Differential enthalpic analysis of the thermal degradation of aromatic and heteroaromatic amino acids provides thermograms which are characteristic of specific amino acids (e.g. phenylalanine, tyrosine, tryptophan or histidine). Curve resolution of the resulting thermograms suggests that a minimum of three reactions are involved in the degradation (within the temperature limits of 500–620 [ddot]K) and provides T_M values for each of these concurrent reactions.     

Dimethylsilicon(IV) Derivatives of Amino Acids

Reactions of dichlorodimethylsilane with the sodium salt of amino acids in 1:2 molar ratio led to the formation of a new series of dimethylsilicon(IV) complexes of general formula, Me 2 SiL 2 [L = anion of amino acids, viz. glycine (HGly), L-methionine (L-MethH), DL- f -alanine (DL- f -AlaH) L-leucine (L-LeuH), L-valine (L-ValH) and D-phenylalanine (D-PheH)]. The complexes have been characterized by elemental analyses, molar conductance, and electronic spectra, and the bonding in these complexes is discussed in terms of their infrared, 1 H and 13 C NMR spectra. A distorted octahedral structure with trans methyl groups has been tentatively suggested for the complexes. The complexes, found soluble in DMSO, have been tested in vitro against various bacteria, viz. Escherichia coli , Pseudomonas putida-2252 , Aeromonas formicans , Staphylococcus aureus-740 , and fungi, viz. Aspergillus niger ORS-4, Aureobasidium pullulans-1991 , Verticillium dahliae-2063 , and Penicillium notatum-1348 .     

Creating a Defined Chirality in Amino Acids and Cyclic Dipeptides by Photochemical Deracemization

2,5-Diketopiperazines are cyclic dipeptides displaying a wide range of applications. Their enantioselective preparation has now been found possible from the respective racemates by a photochemical deracemization (53 examples, 74 % to quantitative yield, 71–99 % ee). A chiral benzophenone catalyst in concert with irradiation at λ=366 nm enables to establish the configuration at the stereogenic carbon atom C6 at will. If other stereogenic centers are present in the diketopiperazines they remain unaffected and a stereochemical editing is possible at a single position. Consecutive reactions, including the conversion into N-aryl or N-alkyl amino acids or the reduction to piperazines, occur without compromising the newly created stereogenic center. Transient absorption spectroscopy revealed that the benzophenone catalyst processes one enantiomer of the 2,5-diketopiperazines preferentially and enables a reversible hydrogen atom transfer that is responsible for the deracemization process. The remarkably long lifetime of the protonated ketyl radical implies a yet unprecedented mode of action.     

Synthesis of Levulinic Acids From Muconic Acids in Hot Water

Levulinic acid is a key biorenewable platform molecule. Its current chemical production from sugars is plagued by limited yields, char formation and difficult separations. An alternative and selective route starting from muconic acid via simple heating in water at high temperature (180 °C) has been developed. Muconic acid can be obtained from sugars or catechol fermentation. Chemical oxidation of catechol is another possibility which advantageously can also be applied on substituted catechols, hereby providing substituted muconic acids. When applying the disclosed hydrothermal protocol on these substrates hitherto unknown substituted levulinic acids were accessed. In particular, 3-propyllevulinic acid has been synthesized from 4-propylcatechol, prepared from pine wood. This propylated derivative has been used for the synthesis of a 3-propyllevulinate diester, i.e. butane-1,4-diyl bis(4-oxo-3-propylpentanoate), via esterification with 1,4-butanediol. The diester showed superior performance as plasticizer in comparison to the corresponding levulinate diester in both PVC (polyvinyl chloride) and PLA (polylactic acid). It plasticizes equally effective as the notorious commercial phthalate-based benchmark DEHP (di-2-ethylhexyl phthalate) in PVC.     

Enantioselective Extraction of Dinitrophenyl Amino Acids Mediated by Lipophilic Deoxyguanosine Derivatives: Chiral Discrimination by Self-Assembly

The transfer of potassium salts of dinitrophenyl amino acids from water to chloroform by the lipophilic guanosine derivative 1 takes place enantioselectively. Depending on the K⁺: 1 ratio, G-quartets of 1 self-assemble into octamers ( O ) or polymers.     

Use of Micelles in the TLC Separation of Polynuclear Aromatic Compounds and Amino Acids

Abstract

The polynuclear aromatic compounds (PNA): anthracene, napthalene, phenanthrene, pyrene, pyrenecarboxaldehyde, benzo (a) pyrene, benzo (e) pyrene, perylene and fluorene can be chromatographed on polyamide TLC sheets using an aqueous micellar solution cf sodium dodecylsulfate (SDS) as the mobile phase. Reversed micellar solutions (of sodium dioctylsulfosuccinate) were used in a reverse phase chromatographic separation of amino acids. Some amino acids tended to streak slightly rather than move as discrete spots. Conditions could be adjusted, however, so that most of the amino acids and all PNA's would move as spots.     

The Study of UV and VIS Absorption Spectra of the Complexes of Amino Acids with Ninhydrin

Abstract

The analysis of amino acids with post column derivatization using ninhydrin is usually carried out with automatic analyzers at wavelengths of 570 nm (for the quantitation of α-amino acids) and 440 nm (for the imino acids), or at only one wavelength, 520 nm, for the total acid content. The α-amino acids are reported to give an absorption maximum at 570 nm, after complex formation with ninhydrin; and α-imino acids have a γ at 440 nm, 520 nm is a compromise wavelength.

This paper presents a study of the absorption of the complexes of amino acids with ninhydrin between 275 and 700 nm. Two new wavelengths are suggested for use, 290 and 404 nm.

In the near UV (290 nm) all the tested acids show a common absorption maximum and good sensitivities. In the visible region at 404 nm, the sensitivities of the α-amino acids are very similar to those observed at 570 nm. At 520 nm the αamino acids have the lowest sensitivities.

The α-imino acids (proline and oxyproline) show absorption maxima only at 290 nm; after that their sensitivities decrease with increasing wavelength.

The paper offers some practical hints on changing the detector wavelength, and to adapt the HPLC's detector to work at one of these two, newly suggested, bands (290 or 404 nm).     

Synthesis and Characterization of Extended Bis(terpyridine)ruthenium Amino Acids

(Oligopyridine)ruthenium(II) complexes have been widely used in dye sensitized solar cells and other sophisticated optical devices due to their outstanding photophysical properties and their chemical stability. Herein, we describe the longitudinal extension of our previously reported bis(terpyridine)ruthenium(II) amino acid [Ru(tpy–NH₂)(tpy–COOH)]²⁺ (tpy = 4′‐substituted 2,2′:6′,2″‐terpyridine) by insertion of para‐phenylene spacers –C₆H₄– between the terpyridine and the functional groups. The influence of the para‐phenylene spacer on the absorption and emission properties is investigated using UV/Vis absorption and emission spectroscopy and is discussed within a qualitative molecular orbital picture.     

游离芳香氨基酸和半胱氨酸对光诱导高铁肌红蛋白还原的影响

肌红蛋白(Myoglobin,Mb)中血红素辅基不仅具有储氧功能,也能吸收特定波长的光而影响蛋白功能表达。实验发现,部分游离的氨基酸对光诱导高铁肌红蛋白(metM b,Fe(III)-Mb)的还原过程及还原程度都有重要作用,因此,本文采用紫外-可见吸收光谱、圆二色谱、三维荧光光谱法,在光照体系中加入拥挤试剂来模拟细胞内拥挤环境,研究芳香氨基酸[色氨酸(Trp)、苯丙氨酸(Phe)、酪氨酸(Tyr)、半胱氨酸(Cys)]对metM b还原的影响。结果表明,含-OH或-SH的氨基酸(Tyr、Cys)能使metM b发生较好的光还原,无-OH或-SH基团的氨基酸(Trp、Phe)对metM b的光还原作用较弱,氨基酸促进metM b光还原的整个过程可能是分子间电子转移的过程。metM b在拥挤环境聚蔗糖70(Ficoll 70)中的光诱导还原程度比在稀溶液中高,拥挤试剂Ficoll70对蛋白的二级结构起保护作用,能够稳定血红素微环境。     

Oxathiaphospholane Approach to the Synthesis of Conjugates of Amino Acids Methyl Esters with Nucleosides

Based upon 1,3,2-oxathiaphospholane chemistry, 5'-O-derivatization of nucleosides with the O-methyl esters of amino acids was performed and corresponding conjugates were obtained in satisfactory yield.     

稻麦中FAO模式必需氨基酸与限制氨基酸比值的研究

本文主要介绍稻麦中按FAO模式比必需氨基酸总量与赖氨酸、苏氨酸含量之间比值的推导过程,并获得其比值分别为6.55和9.00。根据比值可推算样品中按模式比的必需氨基酸总量及赖氨酸含量的最佳理论公式。最后还介绍了上述公式的应用举例。该研究内容不仅为提高稻麦中蛋白质的利用率提供理论依据,而且还为强化食品和饲料的营养研究提供简便的计算方法。     

The Use of A 25 Factorial Design to Study the Effect of Various Alcohols on the Paper Chromatographic Separation of Selected Amino Acids

Abstract

A 2⁵ factorial design was used to evaluate the effect of methanol, ethanol, propanol, butanol and pentanol on the paper chromatographic separation of Arginine, Threonine, Leucine, Histidine, and Tryptophan. The most significant effects occur for the alcohols themselves with an increasing effect with an increase in carbon chain length. The major interaction terms involve the combinations of butanol and pentanol with the other alcohols or with themselves.     

大亚湾沉积物中氨基酸的垂直分布——沉积物柱样W0中的水解氨基酸

测定了采自大亚湾近岸海域的一个长60cm的沉积物柱样W0中15种水解氨基酸的含量；结果表明，15种水解氨基酸含量均随深度而下降，其中苏氨酸、丝氨酸、甘氨酸、丙氨酸、精氨酸、缬氨酸、苯丙氨酸、亮氨酸、异亮氨酸的含量以及水解氨基酸总量随深度的变化可用指数方程c＝c0e^-kx加以描述；天冬氨酸、谷氨酸、丝氨酸、甘氨酸、丙氨酸和缬氨酸是大亚湾沉积物中最丰富的氨基酸。     

大亚湾沉积物中氨基酸的垂直分布棗沉积物柱样W0中的游离氨基酸

用邻苯二甲醛（OPA）－3－巯基丙酸（3－MPA）柱前衍生高效液相色谱法测定了采自大亚湾近岸海域的一个长60cm的沉积物柱样W0中15种游离氨基酸（FAA）的含量，结果表明，W0中FAA总量在0．83－2．69mmol/kg之间，15种FAA以及FAA总量均随深度而以指数曲线降低，对氨基酸组成的分析表明，天冬氨酸，甘氨酸，组氨酸和苯丙氨酸的摩尔分数随深度而上升，苏氨酸，精氨酸，缬氨酸和异亮氨酸的摩尔分数随浓度而下降，其他氨基酸的摩尔分数随深度无显著变化，甘氨酸，丙氨酸，天冬氨酸，谷氨酸，丝氨酸是W0中含量最丰富的氨基酸，其摩尔数依次为28．1％，16．0％，14．7％，10．6％和7．2％。     

Thermodynamics of Transfer of Amino Acids from Water to Aqueous Sodium Sulfate

Abstract

The solubilities of amino acids at 288.15, 298.15 and 308.15K in water and aqueous sodium sulfate have been determined as a function of electrolyte concentration (0.5, 1.0, 1.5 mol/kg of water). It has been observed that sodium sulfate renders amino acids less scluble. The free energies of transfer of amino acids from water to aqueous sodium sulfate have been calculated from the solubility data. The enthalpies and entropies of transfer have also been estimated. The solubility and the thermodynamics of transfer data manifest that sodium sulfate generates favourable interaction between nonpolar groups of amino acids. If applied to proteins, it seems to stabilize the protein native globular structure by enhancing the intramolecular nonpolar-nonpolar group interactions.     

制药废液中氨基酸的分离与测定

为测定维生素 B12 制药厂排出的废液中氨基酸量,先在所取的废液样品中加入乙酸铅使其中蛋白质及其他大分子有机物产生沉淀并用离心法分离.上层澄清液中的氨基酸通过装有强酸性阳离子交换树脂的交换柱(25 cm×2.5 cm)予以分离,用1 mol·L-1 氨水将氨基酸从柱上洗脱.在所得洗脱液中用气相色谱-质谱及傅立叶变换红外光谱法对氨基酸进行定性及定量测定.     

Controlled Genetic Encoding of Unnatural Amino Acids in a Protein Nanopore

Conventional protein engineering methods for modifying protein nanopores are typically limited to 20 natural amino acids, which restrict the diversity of the nanopores in structure and function. To enrich the chemical environment inside the nanopore, we employed the genetic code expansion (GCE) technique to site-specifically incorporate the unnatural amino acid (UAA) into the sensing region of aerolysin nanopores. This approach leveraged the efficient pyrrolysine-based aminoacyl-tRNA synthetase-tRNA pair for a high yield of pore-forming protein. Both molecular dynamics (MD) simulations and single-molecule sensing experiments demonstrated that the conformation of UAA residues provided a favorable geometric orientation for the interactions of target molecules and the pore. This rationally designed chemical environment enabled the direct discrimination of multiple peptides containing hydrophobic amino acids. Our work provides a new framework for endowing nanopores with unique sensing properties that are difficult to achieve using classical protein engineering approaches.