Posttranslational Chemical Mutagenesis Methods to Insert Posttranslational Modifications into Recombinant Proteins

Posttranslational modifications (PTMs) dramatically expand the functional diversity of the proteome. The precise addition and removal of PTMs appears to modulate protein structure and function and control key regulatory processes in living systems. Deciphering how particular PTMs affect protein activity is a current frontier in biology and medicine. The large number of PTMs which can appear in several distinct positions, states, and combinations makes preparing such complex analogs using conventional biological and chemical tools challenging. Strategies to access homogeneous and precisely modified proteins with desired PTMs at selected sites and in feasible quantities are critical to interpreting their molecular code. Here, we summarize recent advances in posttranslational chemical mutagenesis and late-stage functionalization chemistry to transfer novel PTM mimicry into recombinant proteins with emphasis on novel transformations.     

Characterization of Volatile Flavor Compounds in Supercritical Fluid Separated and Identified in Gurum (Citrulluslanatus Var. colocynthoide) Seed Oil Using HSME and GC–MS

In this study, the volatile compound profiles of gurum seed oil were determined using two methods: supercritical CO₂ extraction (SFE) and the screw press process (SPP). For volatile compounds extraction and identification, headspace solid-phase micro-extraction (HS-SPME) and GC–MS were used, respectively. A total number of 56 volatile compounds were revealed and identified in oil extracted by SFE, while only 40 compounds were detected in extracted oil by SPP. Acids, aldehydes, esters, ketones, furans, and other components were present in the highest ratio in oil extracted by SFE. In contrast, alcohols and alkenes were found in the highest proportion in oil extracted by SPP. In this study, it was observed that SFE showed an increase in the amounts of volatile compounds and favorably impacted the aroma of gurum seed oil. The results reveal that different extraction methods significantly impact the volatile components of gurum seed oil, and this study can help evaluate the quality of the oil extracted from gurum seeds.     

Interaction of CO2 with MnOx/Pd(111) Reverse Model Catalytic Interfaces

Understanding the activation of CO₂ on the surface of the heterogeneous catalysts comprised of metal/metal oxide interfaces is of critical importance since it is not only a prerequisite for converting CO₂ to value-added chemicals but also often, a rate-limiting step. In this context, our current work focuses on the interaction of CO₂ with heterogeneous bi-component model catalysts consisting of small MnO_x clusters supported on the Pd(111) single crystal surface. These metal oxide-on-metal ‘reverse’ model catalyst architectures were investigated via temperature programmed desorption (TPD) and x-ray photoelectron spectroscopy (XPS) techniques under ultra-high vacuum (UHV) conditions. Enhancement of CO₂ activation was observed upon decreasing the size of MnO_x nanoclusters by lowering the preparation temperature of the catalyst down to 85 K. Neither pristine Pd(111) single crystal surface nor thick (multilayer) MnO_x overlayers on Pd(111) were not capable of activating CO₂, while CO₂ activation was detected at sub-monolayer (∼0.7 ML) MnO_x coverages on Pd(111), in correlation with the interfacial character of the active sites, involving both MnO_x and adjacent Pd atoms.     

Computer simulation of the formation of polymer networks

Complex crosslinked polymer structures can be quite easily modeled with the aid of computers. BTOSYM's implementation of an algorithm that has been developed by Eichinger and his co-workers over the last few years is described. This algorithm allows us to model both random (as in sulfur-cured rubber) and site-specific (as in end-linked silicones) crosslinking reactions. The simulation method provides detailed information on gel points, cycle rank, modulus of elasticity and other characteristics of the networks as they are formed. Illustrative results obtained with the program are presented.     

Ionic liquid incorporated SPEEK/Chitosan solid polymer electrolytes: ionic conductivity and dielectric study

Journal of Solid State Electrochemistry - In this study, polymeric membranes composed of ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate supported sulfonated poly(ether ether...     

Chemical Modification of a Bacterial Siderophore by a Competitor in Dual-Species Biofilms

Chemical communication between competing bacteria in multi-species environments often enables both species to adapt and survive, and perhaps even thrive. P. aeruginosa and S. aureus are two bacterial pathogens found in natural biofilms, especially in the lungs of cystic fibrosis (CF) patients, where recent studies showed that there is often cooperation between the two species, leading to increased disease severity and antibiotic resistance. However, the mechanisms behind this cooperation are poorly understood. In this study, we analyzed co-cultured biofilms in various settings, and we applied untargeted mass spectrometry-based metabolomics analyses, combined with synthetic validation of candidate compounds. We unexpectedly discovered that S. aureus can convert pyochelin into pyochelin methyl ester, an analogue of pyochelin with reduced affinity for iron (III). This conversion allows S. aureus to coexist more readily with P. aeruginosa and unveils a mechanism underlying the formation of robust dual-species biofilms.