The role of the Aspergillus nidulans high mobility group B protein HmbA, the orthologue of Saccharomyces cerevisiae Nhp6p

The mammalian HMGB1 is a high-mobility-group B protein, which is both an architectural and functional element of chromatin. Nhp6p, the extensively studied fungal homologue of HMGB1 in Saccharomyces cerevisiae has pleiotropic physiological functions. Despite the existence of Nhp6p orthologues in filamentous ascomycetes, little is known about their physiological roles besides their contribution to sexual development. Here we study the function of HmbA, the Aspergillus nidulans orthologue of Nhp6p. We show that HmbA influences the utilization of various carbon- and nitrogen sources, stress tolerance, secondary metabolism, hyphae elongation and maintenance of polarized growth. Additionally, by conducting heterologous expression studies, we demonstrate that HmbA and Nhp6p are partially interchangeable. HmbA restores SNR6 transcription and fitness of nhp6AΔBΔ mutant and reverses its heat sensitivity. Nhp6Ap complements several phenotypes of hmbAΔ, including ascospore formation, utilization of various carbon- and nitrogen-sources, radial growth rate, hypha elongation by polarized growth. However, Nhp6Ap does not complement sterigmatocystin production in a hmbAΔ strain. Finally, we also show that HmbA is necessary for the normal expression of the endochitinase chiA, a cell wall re-modeller that is pivotal for the normal mode of maintenance of polar growth.

Tunable Magnetic Hyperthermia Properties of Pristine and Mildly Reduced Graphene Oxide/Magnetite Nanocomposite Dispersions

We present a study on the magnetic hyperthermia properties of graphene oxide/magnetite (GO/MNP) nanocomposites to investigate their heat production behavior upon the modification of the oxidation degree of the carbonaceous host. Avoiding the harsh chemical conditions of the regular in situ co-precipitation-based routes, the oppositely charged MNPs and GO nanosheets were combined by the heterocoagulation process at pH ~ 5.5, which is a mild way to synthesize composite nanostructures at room temperature. Nanocomposites prepared at 1/5 and 1/10 GO/MNP mass ratios were reduced by NaBH₄ and L-ascorbic acid (LAA) under acidic (pH ~ 3.5) and alkaline conditions (pH ~ 9.3). We demonstrate that the pH has a crucial effect on the LAA-assisted conversion of graphene oxide to reduced GO (rGO): alkaline reduction at higher GO loadings leads to doubled heat production of the composite. Spectrophotometry proved that neither the moderately acidic nor alkaline conditions promote the iron dissolution of the magnetic core. Although the treatment with NaBH₄ also increased the hyperthermic efficiency of aqueous GO/MNP nanocomposite suspensions, it caused a drastic decline in their colloidal stability. However, considering the enhanced heat production and the slightly improved stability of the rGO/MNP samples, the reduction with LAA under alkaline condition is a more feasible way to improve the hyperthermic efficiency of magnetically modified graphene oxides.

Antibiotic-resistant bacteria show widespread collateral sensitivity to antimicrobial peptides

Antimicrobial peptides are promising alternative antimicrobial agents. However, little is known about whether resistance to small-molecule antibiotics leads to cross-resistance (decreased sensitivity) or collateral sensitivity (increased sensitivity) to antimicrobial peptides. We systematically addressed this question by studying the susceptibilities of a comprehensive set of 60 antibiotic-resistant Escherichia coli strains towards 24 antimicrobial peptides. Strikingly, antibiotic-resistant bacteria show a high frequency of collateral sensitivity to antimicrobial peptides, whereas cross-resistance is relatively rare. We identify clinically relevant multidrug-resistance mutations that increase bacterial sensitivity to antimicrobial peptides. Collateral sensitivity in multidrug-resistant bacteria arises partly through regulatory changes shaping the lipopolysaccharide composition of the bacterial outer membrane. These advances allow the identification of antimicrobial peptide-antibiotic combinations that enhance antibiotic activity against multidrug-resistant bacteria and slow down de novo evolution of resistance. In particular, when co-administered as an adjuvant, the antimicrobial peptide glycine-leucine-amide caused up to 30-fold decrease in the antibiotic resistance level of resistant bacteria. Our work provides guidelines for the development of efficient peptide-based therapies of antibiotic-resistant infections.

Target-specific NMR detection of protein-ligand interactions with antibody-relayed 15N-group selective STD

Fragment-based drug design has been successfully applied to challenging targets where the detection of the weak protein-ligand interactions is a key element. ¹H saturation transfer difference (STD) NMR spectroscopy is a powerful technique for this work but it requires pure homogeneous proteins as targets. Monoclonal antibody (mAb)-relayed ¹⁵N-GS STD spectroscopy has been developed to resolve the problem of protein mixtures and impure proteins. A ¹⁵N-labelled target-specific mAb is selectively irradiated and the saturation is relayed through the target to the ligand. Tests on the anti-Gal-1 mAb/Gal-1/lactose system showed that the approach is experimentally feasible in a reasonable time frame. This method allows detection and identification of binding molecules directly from a protein mixture in a multicomponent system.