Serviceability of Fabric Blends of New and Reclaimed Wool (A Progress Report)

What is the wearing quality of garments made from blends of new and reclaimed wool? How do they compare with clothes made from all new wool? That percentage of\u27 reclaimed wool may be used in a fabric without seriously decreasing its serviceability? These are a few of the questions in the minds of many homemakers today as they buy clothes for their families. They realize that wool manufacturers are now making a common practice of extending their stock of new wool by blending it with reclaimed wool. They also know that these manufacturers are required by law to indicate in the form of labels the percentage of each type or wool used in any product containing wool

Facile and selective N-alkylation of gentamicin antibiotics via chemoenzymatic synthesis

The rise and spread of antimicrobial resistance has necessitated the development of novel antimicrobials which are effective against drug resistant pathogens. Aminoglycoside antibiotics (AGAs) remain one of our most effective classes of bactericidal drugs. However, they are challenging molecules to selectively modify by chemical synthesis, requiring the use of extensive protection and deprotection steps leading to long, atom- and step-inefficient synthetic routes. Biocatalytic and chemoenzymatic approaches for the generation of AGA derivatives are of interest as they allow access to more concise and sustainable synthetic routes to novel compounds. This work presents a two-step chemoenzymatic route to regioselectively modify the C-6′ position of AGAs. The approach uses a transaminase enzyme to generate an aldehyde on the C-6′ position in the absence of protecting groups, followed by reductive amination to introduce substituents selectively on this position. Seven candidate transaminases were tested for their ability to deaminate a panel of commercially available AGAs. The C-6′ transaminases could deaminate both pseudo di- and trisaccharide AGAs and tolerate the presence or absence of hydroxyl groups on the C-3′- and C-4′-positions. Additionally, sugar substituents on the C-6 hydroxyl were accepted but not on the C-5 hydroxyl. The most promising enzyme, GenB4, was then coupled with a reductive amination step to synthesise eleven novel 6′-gentamicin C1a analogues with conversions of 13–90%. Five of these compounds were active antimicrobials and four of these retained activity against an aminoglycoside-resistant Escherichia coli. This approach allows facile and step-efficient access to novel aminoglycoside compounds under mild reaction conditions and could potentially enable the development of greener, sustainable, and more cost-effective syntheses of novel AGAs

Natural transaminase fusions for biocatalysis

Biocatalytic approaches are used widely for the synthesis of amines from abundant or low cost starting materials. This is a fast-developing field where novel enzymes and enzyme combinations emerge quickly to enable the production of new and complex compounds. Natural multifunctional enzymes represent a part of multi-step biosynthetic pathways that ensure a one-way flux of reactants. In vivo, they confer a selective advantage via increased reaction rates and chemical stability or prevention of toxicity from reactive intermediates. Here we report the identification and analysis of a natural transaminase fusion, PP_2782, from Pseudomonas putida KT2440, as well as three of its thermophilic homologs from Thermaerobacter marianensis, Thermaerobacter subterraneus, and Thermincola ferriacetica. Both the fusions and their truncated transaminase-only derivatives showed good activity with unsubstituted aliphatic and aromatic aldehydes and amines, as well as with a range of α-keto acids, and L-alanine, L-glutamate, and L-glutamine. Through structural similarity, the fused domain was recognised as the acyl-[acyl-carrier-protein] reductase that affects reductive chain release. These natural transaminase fusions could have a great potential for industrial applications

Mechanoenzymatic reactions with whole cell transaminases: shaken, not stirred

Mechanochemical reactions have emerged in recent years as a green synthetic method because reactions can be performed more rapidly and using less solvent than traditional synthetic approaches. To date, very few mechanoenzymatic reactions have been described. For the first time, transaminases, which are widely used for the amination of aldehydes and ketones, have been used here under mechanoenzymatic conditions to produce amines using significantly less aqueous medium than conventional biocatalytic reactions. The direct use of whole cells was also possible and shorter reaction times could be used to provide amines efficiently with high yields and stereoselectivities

Stereoselective Transaminase-Mediated Synthesis of Serotonin and Melatonin Receptor Agonists

Transaminase enzymes have significant potential for the stereoselective synthesis of drugs or drug precursors. Here, starting from one prochiral β-tetralone, a short and efficient chemoenzymatic synthesis of four agonists of the serotonin/melatonin receptors have been developed. The key step is the stereoselective transamination of the prochiral ketone to produce both enantiomers of 8-methoxy-2-aminotetraline in high yields and enantiomeric excesses. This was followed by either amidation to give the 8-methoxy-2-acetimidotetralines or several facile chemical steps to the 8-hydroxy-2-aminodipropyltetralines

The use of tyrosinases in a chemoenzymatic cascade as a peptide ligation strategy

Peptides play many key roles in biological systems and numerous methods have been developed to generate both natural and unnatural peptides. However, straightforward, reliable coupling methods that can be achieved under mild reactions conditions are still sought after. In this work, a new N-terminal tyrosine-containing peptide ligation method with aldehydes, utilising a Pictet–Spengler reaction is described. In a key step, tyrosinase enzymes have been used to convert L-tyrosine to L-3,4-dihydroxyphenyl alanine (L-DOPA) residues, generating suitable functionality for the Pictet–Spengler coupling. This new chemoenzymatic coupling strategy can be used for fluorescent-tagging and peptide ligation purposes

Within- and between-person variability of exhaled breath condensate pH and NH4+ in never and current smokers

SummaryRecent studies have suggested that the collection of exhaled breath condensate (EBC) may be a viable method in occupational field studies to sample secretions of the lower airway because it is simple to perform and non-invasive. However, there are unresolved questions about whether certain laboratory conditions may influence the analysis of EBC biomarker measurements. A total of 12 subjects performed 116 EBC tests. The effect of short and long-term sample storage and sample volume on two biomarkers of acid stress, pH and NH4+, in EBC were investigated and did not significantly influence either marker measurement after argon deaeration. We also investigated the variability and the effect of smoking on the biomarkers by collecting six samples each from five adult never smokers and five adult current smokers over a period of 1 month (n=60 total). For pH, the within-person and between-person variability was larger in current smokers compared to never smokers. Similar results were found for NH4+. Cigarette packs smoked per day now was also associated with both pH (p=0.01) and NH4+ (p=0.04) using mixed effects regression analysis. The variability and smoking results suggest that repeated measurements of EBC pH and NH4+ from the same individual may accurately predict the biological state of the airways of current smokers when compared to never smokers

Enzymatic synthesis of benzylisoquinoline alkaloids using a parallel cascade strategy and tyrosinase variants

Benzylisoquinoline alkaloid derived pharmaceuticals are widely applied in modern medicines. Recent studies on the microbial production of benzylisoquinolines have highlighted key biological syntheses towards these natural products. Routes to non-natural benzylisoquinolines have been less explored, particularly halogenated compounds which are more challenging. Here, we show the use of a tyrosinase, tyrosine decarboxylase, transaminase, and norcoclaurine synthase which are combined in a parallel cascade design, in order to generate halogenated benzylisoquinoline alkaloids in high enantiomeric excess. Notably, mutagenesis studies are applied to generate tyrosinase mutants, which enhance the acceptance of halogenated tyrosines for use in the biocatalytic cascades developed

A theoretical study of the response of vascular tumours to different types of chemotherapy

In this paper we formulate and explore a mathematical model to study continuous infusion of a vascular tumour with isolated and combined blood-borne chemotherapies. The mathematical model comprises a system of nonlinear partial differential equations that describe the evolution of the healthy (host) cells, the tumour cells and the tumour vasculature, coupled with distribution of a generic angiogenic stimulant (TAF) and blood-borne oxygen. A novel aspect of our model is the presence of blood-borne chemotherapeutic drugs which target different aspects of tumour growth (cf. proliferating cells, the angiogenic stimulant or the tumour vasculature). We run exhaustive numerical simulations in order to compare vascular tumour growth before and following therapy. Our results suggest that continuous exposure to anti-proliferative drug will result in the vascular tumour being cleared, becoming growth-arrested or growing at a reduced rate, the outcome depending on the drug’s potency and its rate of uptake. When the angiogenic stimulant or the tumour vasculature are targeted by the therapy, tumour elimination can not occur: at best vascular growth is retarded and the tumour reverts to an avascular form. Application of a combined treatment that destroys the vasculature and the TAF, yields results that resemble those achieved following successful treatment with anti-TAF or anti-vascular therapy. In contrast, combining anti-proliferative therapy with anti-TAF or antivascular therapy can eliminate the vascular tumour. In conclusion, our results suggest that tumour growth and the time of tumour clearance are highly sensitive to the specific combinations of anti-proliferative, anti-TAF and anti-vascular drugs

A transaminase-mediated aldol reaction and applications in cascades to styryl pyridines

Transaminase enzymes are well established biocatalysts that are used in chemical synthesis due to their beneficial sustainability profile, regio- and stereoselectivity and substrate specificity. Here, the use of a wild-type Chromobacterium violaceum transaminase (CvTAm) in enzyme cascades revealed the formation of a novel hydroxystyryl pyridine product. Subsequent studies established it was a transaminase mediated reaction where it was exhibiting apparent aldolase reactivity. This promiscuous enzyme reaction mechanism was then explored using other wild-type transaminases and via the formation of CvTAm mutants. Application of one pot multi-step enzyme cascades was subsequently developed to produce a range of hydroxystyryl pyridines