Redox potential tuning by calcium ions in a novel c-type cytochrome from an anammox organism.

The electrochemical potentials of redox-active proteins need to be tuned accurately to the correct values for proper biological function. Here, we describe a diheme cytochrome c with high heme redox potentials of about +350 mV, despite having a large overall negative charge, which typically reduces redox potentials. High-resolution crystal structures, spectroelectrochemical measurements, and high-end computational methods show how this is achieved: each heme iron has a calcium cation positioned next to it at a distance of only 6.

Measurements of Intra- and Extra-Cellular 5-Methyltetrahydrofolate Indicate that DSM 20083 and DSM 20438 Do Not Actively Excrete 5-Methyltetrahydrofolate .

Certain intestinal bifidobacteria have the ability to synthesize folates. experiments revealed a high production, cellular accumulation, and release of reduced folate vitamers like 5-methyltetrahydrofolate and tetrahydrofolate in folate-free medium (FFM). However, it is still unclear to which extent synthesized folates are polyglutamylated and probably not available for transport, and if they are actively released by excretion.

Development of stable isotope dilution assays for the quantitation of intra- and extracellular folate patterns of Bifidobacterium adolescentis.

Folate-producing bifidobacteria have been studied extensively but appropriate methods for detailed quantitation of intra- and extracellular pteroylmono- and pteroylpolyglutamate patterns are lacking. Therefore, B. adolescentis DSM 20083 was cultivated in folate-free medium (FFM) for 24h to develop and validate stable isotope dilution assays (SIDAs) coupled with LC-MS/MS for the determination of 5-formyltetrahydrofolic acid (5-HCO-Hfolate), 10-formylfolic acid (10-HCO-PteGlu), tetrahydrofolic acid (Hfolate), folic acid (PteGlu) and 5-methyltetrahydrofolic acid (5-CH-Hfolate) including its di-, tri-, and tetraglutamic vitamers (5-CH-HPteGlu).