A new rhodamine‐based fluorescent chemodosimeter for mercuric ions in water media

A new rhodamine–ethylenediamine–nitrothiourea conjugate (RT) was synthesized and its sensing property as a fluorescent chemodosimeter toward metal ions was explored in water media. Analytical results from absorption and fluorescence spectra revealed that the addition of Hg²⁺ ions to the aqueous solution of the chemodosimeter RT caused a distinct fluorescence OFF–ON response with a remarkable visual color change from colorless to pink; however, no clear spectral and color changes were observed from other metal ions including: Zn²⁺, Cu²⁺, Cd²⁺, Pb²⁺, Ag⁺, Fe²⁺, Cr³⁺, Co³⁺, Ni²⁺, Ca²⁺, Mg²⁺, K⁺ and Na⁺. The sensing results and the molecular structure suggested that a Hg²⁺‐induced a desulfurization reaction and cyclic guanylation of the thiourea moiety followed by ring‐opening of the rhodamine spirolactam in RT are responsible for a distinct fluorescence turn‐on signal, indicating that RT is a remarkably sensitive and selective chemodosimeter for Hg²⁺ ions in aqueous solution. Hg²⁺ within a concentration range from 0.1 to 25 μM can be determined using RT as a chemodosimeter and a detection limit of 0.04 μM is achieved. Copyright © 2014 John Wiley & Sons, Ltd.     

A conserved histidine in human DNLZ/HEP is required for stimulation of HSPA9 ATPase activity

The DNL-type zinc-finger protein DNLZ regulates the activity and solubility of the human mitochondrial chaperone HSPA9. To identify DNLZ residues that are critical for chaperone regulation, we carried out an alanine mutagenesis scan of charged residues in a W115I mutant of human DNLZ and assessed the effect of each mutation on interactions with HSPA9. All mutants analyzed promote the solubility of HSPA9 upon expression in Escherichia coli. However, binding studies examining the effect of DNLZ mutants on chaperone tryptophan fluorescence identified three mutations (R81A, H107A, and D111A) that decrease DNLZ binding affinity for nucleotide-free chaperone. In addition, ATPase measurements revealed that DNLZ–R81A and DNLZ–D111A both stimulate the catalytic activity HSPA9, whereas DNLZ–H107A does not elicit an increase in activity even when present at a concentration that is 10-fold higher than the level required for half-maximal stimulation by DNLZ. These findings implicate a conserved histidine as critical for DNLZ regulation of mitochondrial HSPA9 catalytic activity.     

In vivo and in vitro analyses of toxic mutants of HET-s: FTIR antiparallel signature correlates with amyloid toxicity

The folding and interactions of amyloid proteins are at the heart of the debate as to how these proteins may or may not become toxic to their host. Although little is known about this issue, the structure seems to be clearly involved with effects on molecular events. To understand how an amyloid may be toxic, we previously generated a yeast toxic amyloid (mutant 8) from the nontoxic HET-s_(218-289) prion domain of Podospora anserina. Here, we performed a comprehensive structure-toxicity study by mutating individually each of the 10 mutations found in mutant 8. The study of the library of new mutants generated allowed us to establish a clear link between Fourier transform infrared antiparallel signature and amyloid toxicity. All of the mutants that form parallel β-sheets are not toxic. Double mutations may be sufficient to shift a parallel structure to antiparallel amyloids, which are toxic to yeast. Our findings also suggest that the toxicity of antiparallel structured mutants may be linked to interaction with membranes.     

Nef-mediated resistance of human immunodeficiency virus type 1 to antiviral cytotoxic T lymphocytes.

Although Nef has been proposed to effect the escape of human immunodeficiency virus type 1 (HIV-1) from cytotoxic T lymphocytes (CTL) through downmodulation of major histocompatibility complex class I molecules, little direct data have been presented previously to support this hypothesis. By comparing nef-competent and nef-deleted HIV-1 strains in an in vitro coculture system, we demonstrate that the presence of this viral accessory gene leads to impairment of the ability of HIV-1-specific CTL clones to suppress viral replication. Furthermore, inhibition by genetically modified CTL that do not require major histocompatibility complex class I-presented antigen (expressing the CD4 T-cell receptor [TCR] zeta-chain hybrid receptor) is similar for both nef-competent and -deleted strains, indicating that Nef does not impair the effector functions of CTL but acts at the level of TCR triggering. In contrast, we note that another accessory gene, vpr, does not induce resistance of HIV-1 to suppression by CTL clones. We conclude that Nef (and not Vpr) contributes to functional HIV-1 immune evasion and that this effect is mediated by diminished antigen presentation to CTL.     

Serum beta 2 microglobulin in adult myeloid acute leukemias

Serum beta 2 microglobulin levels, measured by radioimmunoassay (Phadebas test), were found increased in acute myeloid leukemias at diagnosis. Serum beta 2 microglobulin levels were significantly higher in patients with monocytic leukemias (13 patients, M4-M5 FAB classification) than in those with other cytological types (18 patients). Beta 2 microglobulin levels at diagnosis were correlated with serum lysozyme levels, but they were not correlated with blood blast counts, serum LDH and ferritin levels. 195 serum beta 2 microglobulin measurements were made serially in 30 patients with acute myeloid leukemias in first remission. Compared to values at diagnosis, beta 2 microglobulin levels in remission were significantly decreased. Out of 30 patients in remission 12 had increased serum beta 2 microglobulin levels (greater than 3 mg/l). Serial measurements were not predictive for relapses.