No abstract

To investigate a novel branch of the shikimate biosynthesis pathway operating in the formation of 3-amino-5-hydroxybenzoic acid (AHBA), the unique biosynthetic precursor of rifamycin and related ansamycins, a series of target-directed mutations and heterologous gene expressions were investigated in Amycolatopsis mediterranei and Streptomyces coelicolor. The genes involved in AHBA formation were inactivated individually, and the resulting mutants were further examined by incubating the cell-free extracts with known intermediates of the pathway and analyzing for AHBA formation. The rifL, -M, and -N genes were shown to be involved in the step ( . Mutants of the rifH and -J genes produced rifamycin B at 1% and 10%, respectively, of the yields of the wild type; inactivation of the rifG gene did not affect rifamycin production significantly. Finally, coexpressing the rifG-N and -J genes in S. coelicolor YU105 under the control of the act promoter led to significant production of AHBA in the fermented cultures, confirming that seven of these genes are indeed necessary and sufficient for AHBA formation. The effects of deletion of individual genes from the heterologous expression cassette on AHBA formation duplicated the effects of the genomic rifG-N and -J mutations on rifamycin production, indicating that all these genes encode proteins with catalytic rather than regulatory functions in AHBA formation for rifamycin biosynthesis by A. mediterranei.

Correlating the optical properties to the magnetic properties in superparamagnetic iron oxide (Fe 3 O 4 ) nanoparticles (SPIONs) will be a boost for future biomedical applications. However, designing such SPIONs without altering its properties is a real challenge. Here, we demonstrate the engineering of the magnetofluorescent properties simply by tuning the carbon structure in graphitic carbon coated SPIONs. By synthesizing three distinct nanostructures in an easy single step process and studying the in depth structural−functional relationship, we found that the thickness of carbon shell decides the fate of magneto-fluorescent characteristics in SPIONs. Single particle fluorescence data show that the number of emissive photon increases substantially with the increase in the thickness of carbon shell, albeit, the observed relaxivity was enough to get high quality magnetic resonance imaging. The ex vivo magnetic hyperthermia results advanced the use of SPIONs as a single platform for cancer theranostics.

Experimental details, mechanism of CS-2 and N-acylurea, curve fitting, and 1 H NMR spectra used for the present study are given. This material is available free of charge via the Internet at http://pubs.acs.org.

The present study aimed to compare the effects of non-thermal techniques with thermal treatment on physicochemical properties, bioaccessibility, and antioxidant capacity of bioactives in rosehip (Rosa canina) infusions. High pressure processing (HPP) at 200, 400, or 600 MPa for 5 and 15 min; pulsed electric field (PEF) with 5, 10, and 15 kJ/kg specific energy intakes at 1 and 3 kV/cm electric field strength;