Reaction microcalorimetry and potentiometry have been used to define the thermodynamics of assembly of Escherichia coli aspartate transcarbamoylase (aspartate carbamoyltransferase, carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) from its catalytic and regulatory subunits and the linkage between assembly and proton binding. Over the pH range 7-9.5 and the temperature range 15-30...

Pheomelanins, the epidermal pigments of red-haired people responsible for their enhanced UV susceptibility, contain 1,4-benzothiazines and 1,3-benzothiazole as main structural components. Despite the major role played in pheomelanin phototoxicity, the photoreactivity of these species has so far remained unexplored. Static and time-resolved fluorescence spectroscopy was used to identify excited-...

Sterically-stabilized poly(methyl methacrylate) (PMMA) latexes dispersed in nonpolar solvents are a classic, well-studied system in colloid science. This is because they can easily be synthesized with a narrow size distribution and because they interact essentially as hard spheres. These PMMA latexes can be charged using several methods (by adding surfactants, incorporating ionizable groups, or...

The assembly of integral membrane protein complexes is frequently supported by transmembrane domain (TMD) interactions. Here, we present the BLaTM assay that measures homotypic as well as heterotypic TMD-TMD interactions in a bacterial membrane. The system is based on complementation of β-lactamase fragments genetically fused to interacting TMDs, which confers ampicillin resistance to expressin...

Proton diffusion along membrane surfaces is thought to be essential for many cellular processes such as energy transduction. Commonly, it is treated as a succession of jumps between membrane-anchored proton-binding sites. Our experiments provide evidence for an alternative model. We released membrane-bound caged protons by UV flashes and monitored their arrival at distant sites by fluorescence ...

In order to make reliable predictions of the acid-base properties of macroligands with a large number of ionizable sites such as dendrimers, one needs to develop and validate computational methods that accurately estimate the acidity constants (pKa) of their chemical building blocks. In this article, we couple density functional theory (B3LYP) with a Poisson-Boltzmann continuum solvent model to...

To elucidate the functional role of the lysyl residue highly conserved in NAD(P)(+)-dependent amino acid dehydrogenases, Lys-80 of leucine dehydrogenase from Bacillus stearothermophilus has been mutated into Ala, Arg, or Gln. All of the mutant enzymes had markedly reduced activities in the oxidative deamination, whereas the Michaelis constants for substrate and coenzyme did not change significa...

In the context of the SAMPL5 challenge water-cyclohexane distribution coefficients for 53 drug-like molecules were predicted. Four different models based on molecular dynamics free energy calculations were tested. All models initially assumed only one chemical state present in aqueous or organic phases. Model A is based on results from an alchemical annihilation scheme; model B adds a long rang...

Lipid Nanoparticles In article number 2301929, Dan Peer and colleagues developed novel ionizable lipids for improved delivery of mRNA payloads. Rational lipid design together with in vivo screening identified lipid-based nanoparticles (LNPs) enhanced cell trophism. This study suggests that a structural combination tail linker can drive trophism LNPs vivo.