Synthesis of optically pure .alpha.-alkylated .alpha.-amino acids and a single-step method for enantiomeric excess determination [Erratum to document cited in CA108(19):166035p]

ABSTRACT Alcaligenes denitrificans Y2k-2 was obtained by selective enrichment followed by screening from soil samples, which showed ω-amino acid:pyruvate transaminase activity, to kinetically resolve aliphatic β-amino acid, and the corresponding structural gene (aptA) was cloned. The gene was functionally expressed in Escherichia coli BL21 by using an isopropyl-β-d-thiogalactopyranoside (IPTG)-inducible pET expression system (9.6 U/mg), and the recombinant AptA was purified to show a specific activity of 77.2 U/mg for l-β-amino-n-butyric acid (l-β-ABA). The enzyme converts various β-amino acids and amines to the corresponding β-keto acids and ketones by using pyruvate as an amine acceptor. The apparent Km and V max for l-β-ABA were 56 mM and 500 U/mg, respectively, in the presence of 10 mM pyruvate. In the presence of 10 mM l-β-ABA, the apparent Km and V max for pyruvate were 11 mM and 370 U/mg, respectively. The enzyme exhibits high stereoselectivity (E > 80) in the kinetic resolution of 50 mM d,l-β-ABA, producing optically pure d-β-ABA (99% enantiomeric excess) with 53% conversion.

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Purification of Urokinase from Complex Mixtures Using Immobilized Monoclonal Antibody Against Urokinase Light Chain

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657308 ◽

1983 ◽

Vol 49 (01) ◽

pp. 024-027 ◽

Cited By ~ 20

Author(s):

David Vetterlein ◽

Gary J Calton

Keyword(s):

Monoclonal Antibody ◽

Light Chain ◽

Culture Media ◽

Biological Fluids ◽

Single Step ◽

High Yield ◽

Step Method ◽

Commercial Preparation ◽

E Coli ◽

Tissue Culture Media

SummaryThe preparation of a monoclonal antibody (MAB) against high molecular weight (HMW) urokinase light chain (20,000 Mr) is described. This MAB was immobilized and the resulting immunosorbent was used to isolate urokinase starting with an impure commercial preparation, fresh urine, spent tissue culture media, or E. coli broth without preliminary dialysis or concentration steps. Monospecific antibodies appear to provide a rapid single step method of purifying urokinase, in high yield, from a variety of biological fluids.

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Design of Iridium N-Heterocyclic Carbene Amino Acid Catalysts for Asymmetric Transfer Hydrogenation of Aryl Ketones

Catalysts ◽

10.3390/catal11060671 ◽

2021 ◽

Vol 11 (6) ◽

pp. 671

Author(s):

Chad M. Bernier ◽

Joseph S. Merola

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Enantiomeric Excess ◽

Transfer Hydrogenation ◽

Acid Catalysts ◽

Asymmetric Transfer Hydrogenation ◽

Reaction Conditions ◽

Chiral Complexes ◽

Acetophenone Derivatives ◽

Aryl Ketones

A series of chiral complexes of the form Ir(NHC)2(aa)(H)(X) (NHC = N-heterocyclic carbene, aa = chelated amino acid, X = halide) was synthesized by oxidative addition of -amino acids to iridium(I) bis-NHC compounds and screened for asymmetric transfer hydrogenation of ketones. Following optimization of the reaction conditions, NHC, and amino acid ligands, high enantioselectivity was achieved when employing the Ir(IMe)2(l-Pro)(H)(I) catalyst (IMe = 1,3-dimethylimidazol-2-ylidene), which asymmetrically reduces a range of acetophenone derivatives in up to 95% enantiomeric excess.

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A Novel and Efficient Method for the Synthesis of Methyl (R)-10-Hydroxystearate and FAMEs from Sewage Scum

Catalysts ◽

10.3390/catal11060663 ◽

2021 ◽

Vol 11 (6) ◽

pp. 663

Author(s):

Luigi di Bitonto ◽

Valeria D’Ambrosio ◽

Carlo Pastore

Keyword(s):

Fatty Acid Methyl Esters ◽

Methyl Esters ◽

Enantiomeric Excess ◽

Single Step ◽

Acid Catalysts ◽

Acid Methyl ◽

Chloride Hexahydrate ◽

Catalyst Temperature ◽

Homogeneous Acid ◽

Aluminum Chloride Hexahydrate

In this work, the transesterification of methyl estolides (ME) extracted from the lipid component present in the sewage scum was investigated. Methyl 10-(R)-hydroxystearate (Me-10-HSA) and Fatty Acid Methyl Esters (FAMEs) were obtained in a single step. A three-level and four factorial Box–Behnken experimental design were used to study the effects of methanol amounts, catalyst, temperature, and reaction time on the transesterification reaction using aluminum chloride hexahydrate (AlCl3·6H2O) or hydrochloric acid (HCl) as catalysts. AlCl3·6H2O was found quite active as well as conventional homogeneous acid catalysts as HCl. In both cases, a complete conversion of ME into Me-10-HSA and FAMEs was observed. The products were isolated, quantified, and fully characterized. At the end of the process, Me-10-HSA (32.3%wt) was purified through a chromatographic separation and analyzed by NMR. The high enantiomeric excess (ee > 92%) of the R-enantiomer isomer opens a new scenario for the valorization of sewage scum.

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ChemInform Abstract: Asymmetric Synthesis of Unusual Amino Acids: Synthesis of the Optically Pure Isomers of Indole-Protected β-Methyltryptophan Suitable for Peptide Synthesis.

ChemInform ◽

10.1002/chin.199317235 ◽

2010 ◽

Vol 24 (17) ◽

pp. no-no

Author(s):

L. W. BOTEJU ◽

K. WEGNER ◽

V. J. HRUBY

Keyword(s):

Amino Acids ◽

Asymmetric Synthesis ◽

Peptide Synthesis ◽

Unusual Amino Acids ◽

Optically Pure

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Simultaneous determination of the concentration and enantiomeric excess of amino acids with a coumarin-derived achiral probe

Analytical Methods ◽

10.1039/d1ay00271f ◽

2021 ◽

Vol 13 (16) ◽

pp. 1905-1910

Author(s):

Lamei Yang ◽

Feng Luo ◽

Weili Wei

Keyword(s):

Amino Acids ◽

Simultaneous Determination ◽

Enantiomeric Excess ◽

Chiral Analysis

An achiral easy-to-synthesize coumarin aldehyde probe was designed and synthesized for chiral analysis of amino acids.

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A multi-enzyme cascade for efficient production of d-p-hydroxyphenylglycine from l-tyrosine

Bioresources and Bioprocessing ◽

10.1186/s40643-021-00394-2 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Xu Tan ◽

Sheng Zhang ◽

Wei Song ◽

Jia Liu ◽

Cong Gao ◽

...

Keyword(s):

Amino Acids ◽

Specific Activity ◽

Enantiomeric Excess ◽

Efficient Production ◽

Enzyme Cascade ◽

Rate Limiting Step ◽

Limiting Step ◽

Rotation Strategy ◽

Rate Limiting

AbstractIn this study, a four-enzyme cascade pathway was developed and reconstructed in vivo for the production of d-p-hydroxyphenylglycine (D-HPG), a valuable intermediate used to produce β-lactam antibiotics and in fine-chemical synthesis, from l-tyrosine. In this pathway, catalytic conversion of the intermediate 4-hydroxyphenylglyoxalate by meso-diaminopimelate dehydrogenase from Corynebacterium glutamicum (CgDAPDH) was identified as the rate-limiting step, followed by application of a mechanism-guided “conformation rotation” strategy to decrease the hydride-transfer distance d(C6HDAP−C4NNADP) and increase CgDAPDH activity. Introduction of the best variant generated by protein engineering (CgDAPDHBC621/D120S/W144S/I169P with 5.32 ± 0.85 U·mg−1 specific activity) into the designed pathway resulted in a D-HPG titer of 42.69 g/L from 50-g/L l-tyrosine in 24 h, with 92.5% conversion, 71.5% isolated yield, and > 99% enantiomeric excess in a 3-L fermenter. This four-enzyme cascade provides an efficient enzymatic approach for the industrial production of D-HPG from cheap amino acids.

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High-resolution limited-angle phase tomography of dense layered objects using deep neural networks

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1821378116 ◽

2019 ◽

Vol 116 (40) ◽

pp. 19848-19856 ◽

Cited By ~ 12

Author(s):

Alexandre Goy ◽

Girish Rughoobur ◽

Shuai Li ◽

Kwabena Arthur ◽

Akintunde I. Akinwande ◽

...

Keyword(s):

Integrated Circuit ◽

Deep Neural Networks ◽

Tomographic Reconstruction ◽

Synthetic Data ◽

Single Step ◽

Training Set ◽

Step Method ◽

3 Dimensional ◽

Dimensional Reconstruction ◽

Optical Domain

We present a machine learning-based method for tomographic reconstruction of dense layered objects, with range of projection angles limited to ±10○. Whereas previous approaches to phase tomography generally require 2 steps, first to retrieve phase projections from intensity projections and then to perform tomographic reconstruction on the retrieved phase projections, in our work a physics-informed preprocessor followed by a deep neural network (DNN) conduct the 3-dimensional reconstruction directly from the intensity projections. We demonstrate this single-step method experimentally in the visible optical domain on a scaled-up integrated circuit phantom. We show that even under conditions of highly attenuated photon fluxes a DNN trained only on synthetic data can be used to successfully reconstruct physical samples disjoint from the synthetic training set. Thus, the need for producing a large number of physical examples for training is ameliorated. The method is generally applicable to tomography with electromagnetic or other types of radiation at all bands.

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