Rapid sodium periodate cleavage of an unnatural amino acid enables unmasking of a highly reactive α-oxo aldehyde for protein bioconjugation

The α-oxo aldehyde is a highly reactive aldehyde for which many protein bioconjugation strategies exist. Here, we explore the genetic incorporation of a threonine-lysine dipeptide into proteins, harbouring a “masked” α-oxo aldehyde that is rapidly unveiled in four minutes. The reactive aldehyde could undergo site-specific protein modification by SPANC ligation

Metastatic melanoma: An unusual presentation

In this report we describe a case of a malignant cutaneous melanoma metastasizing to the pleural surface and peritoneal cavity 5 years after surgical resection of the primary lesion. Malignant cutaneous melanoma is a very aggressive cancer able to metastasize anywhere in the body. Pleural secondary lesions represent a rare event described only in a small number of patients and the association with peritoneal localizations may suggest an uncommon pattern of spread that we discuss. Free full text available at www.tumorionline.it

Chemical Bioconjugation of Proteins in an Undergraduate Lab: One-Pot Oxidation and Derivatization of the N-Terminus

A laboratory experiment introducing the concept of chemical bioconjugation of proteins to undergraduate students in a therapeutically relevant context was developed. Initially, students installed an aldehyde functionality into a protein via the oxidation of the N-terminal threonine residue of the cholera toxin subunit B (CTB) protein, which was followed by subsequent modification via hydrazone addition under mild conditions with a chromophore bearing a distinct UV–vis-absorption peak. Students determined the yield of the reaction to be ca. 11% by HPLC coupled to UV–vis spectroscopy and developed key skills such as preparation of stock solutions, chemical manipulation of proteins, and analysis via HPLC. The reported experiment can be readily adapted for use with other proteins and may contribute to enhancing constructive alignment in interdisciplinary degree programs at the chemistry–biology interface

Selectivity and stability of N-terminal targeting protein modification chemistries

Protein N-termini provide uniquely reactive motifs for single site protein modification. Though a number of reactions have been developed to target this site, the selectivity, generality, and stability of the conjugates formed has not been studied. We have therefore undertaken a comprehensive comparative study of the most promising methods for N-terminal protein modification, and find that there is no ‘one size fits all’ approach, necessitating reagent screening for a particular protein or application. Moreover, we observed limited stability in all cases, leading to a need for continued innovation and development in the bioconjugation field

Results from the Super Cryogenic Dark Matter Search (SuperCDMS) experiment at Soudan

We report the result of a blinded search for Weakly Interacting Massive Particles (WIMPs) using the majority of the SuperCDMS Soudan dataset. With an exposure of 1690 kg days, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP--nucleon cross section of $1.4 \times 10^{-44}$ ($1.0 \times 10^{-44}$) cm$^2$ at 46 GeV/$c^2$. These results set the strongest limits for WIMP--germanium-nucleus interactions for masses $>$12 GeV/$c^2$

Biocatalytic Transfer of Pseudaminic Acid (Pse5Ac7Ac) Using Promiscuous Sialyltransferases in a Chemoenzymatic Approach to Pse5Ac7Ac-Containing Glycosides

Pseudaminic acid (Pse5Ac7Ac) is a nonmammalian sugar present on the cell surface of a number of bacteria including Pseudomonas aeruginosa, Campylobacter jejuni, and Acinetobacter baumannii. However, the role Pse5Ac7Ac plays in host–pathogen interactions remains underexplored, particularly compared to its ubiquitous sialic acid analogue Neu5Ac. This is primarily due to a lack of access to difficult to prepare Pse5Ac7Ac glycosides. Herein, we describe the in vitro biocatalytic transfer of an activated Pse5Ac7Ac donor onto glycosyl acceptors, enabling the enzymatic synthesis of Pse5Ac7Ac-containing glycosides. In a chemoenzymatic approach, chemical synthesis initially afforded access to a late-stage Pse5Ac7Ac biosynthetic intermediate, which was subsequently converted to the desired CMP-glycosyl donor in a one-pot two-enzyme process using biosynthetic enzymes. Finally, screening a library of 13 sialyltransferases (SiaT) with the unnatural substrate enabled the identification of a promiscuous inverting SiaT capable of turnover to afford β-Pse5Ac7Ac-terminated glycosides.</p

Expanding the scope of the successive ring expansion strategy for macrocycle and medium-sized ring synthesis : unreactive and reactive lactams

New methods are described that expand the scope of the Successive Ring Expansion (SuRE) with respect to synthetically challenging lactams. A protocol has been developed for use with 'unreactive' lactams, enabling SuRE reactions to be performed on subsrates that fail under previously established conditions. Ring expansion is also demonstarted on 'reactive' lactams derived from iminosugars for the first time. The new SuRE methods were used to prepare a diverse array of medium-sized and macrocyclic lactams and lactones, which were evaluted in an anti-bacterial assay against E. coli BW25113WT

Using Automated Glycan Assembly (AGA) for the Practical Synthesis of Heparan Sulfate Oligosaccharide Precursors

Herein we report synthesis of complex heparan sulfate oligosaccharide precursors by automated glycan assembly using disaccharide donor building blocks. Rapid access to a hexasaccharide was achieved through iterative solid phase glycosylations on a photolabile resin using Glyconeer™, an automated oligosaccharide synthesiser, followed by photochemical cleavage and glycan purification using simple flash column chromatography