protein-purification-free-method-binding-affinity-determination

Protein Purification-free Method of Binding Affinity Determination by Microscale Thermophoresis

Quantitative characterization of protein  interactions is essential in practically any field of life sciences,  particularly drug discovery. Most of ...

National Cancer Institute

SAIC-Frederick, Inc.

The role of the central atom X in the structure and reactivity of di-Ru-substituted gamma-Keggin polyoxometalates (POMs), gamma-[(Xn+O4)RuIII2(OH)2(MFM)10O32](8-n)-), where MFM = Mo and W, and X = AlIII, SiIV, PV, and SVI., was computationally investigated. It was shown that for both MFM = Mo and W the nature of X is crucial in determining the lower lying electronic states of the polyoxoanions, which in turn likely significantly impacts their reactivity. For the electropositive X = AlIII, the ground state is a low-spin state, while for the more electronegative X = SVI the ground state is a high-spin state. In other words, the heteroatom X can be an "internal switch" for defining the ground electronic states of the gamma-M2-Keggin POMs. The obtained trends, in general, are less pronounced for MFM = Mo than for W. On the basis of the comparison of the calculated energy gaps between low-spin and high-spin states of polytungstates and polymolybdates, we predict that the gamma-M2-Keggin polytungstates could be more reactive than their polymolybdate analogues. For purposes of experimental verification the computationally predicted and evaluated polytungstate gamma-[(SiO4)RuIII2(OH)2(OH2)2W10O32]4- was prepared and characterized.

The role of the central atom in structure and reactivity of polyoxometalates with adjacent d-electron metal sites. computational and experimental studies of gamma-[(Xn+O4)RuIII2(OH)2(MFM)10O32](8-n)-) for MFM = Mo and W, and X = AlIII, SiIV, PV, and SVI.

Phosphorylation of signal transducer and activator of transcription 3 (STAT3) on a single tyrosine residue in response to growth factors, cytokines, interferons, and oncogenes activates its dimerization, translocation to the nucleus, binding to the interferon Î³ (gamma)-activated sequence (GAS) DNA-binding site and activation of transcription of target genes. STAT3 is constitutively phosphorylated in various cancers and drives gene expression from GAS-containing promoters to promote tumorigenesis. Recently, roles for unphosphorylated STAT3 (U-STAT3) have been described in response to cytokine stimulation, in cancers, and in maintenance of heterochromatin stability. However, the mechanisms underlying U-STAT3 binding to DNA has not been fully investigated. Here, we explore STAT3-DNA interactions by atomic force microscopy (AFM) imaging. We observed that U-STAT3 molecules bind to the GAS DNA-binding site as dimers and monomers. In addition, we observed that U-STAT3 binds to AT-rich DNA sequence sites and recognizes specific DNA structures, such as 4-way junctions and DNA nodes, within negatively supercoiled plasmid DNA. These structures are important for chromatin organization and our data suggest a role for U-STAT3 as a chromatin/genome organizer. Unexpectedly, we found that a C-terminal truncated 67.5-kDa STAT3 isoform recognizes single-stranded spacers within cruciform structures that also have a role in chromatin organization and gene expression. This isoform appears to be abundant in the nuclei of cancer cells and, therefore, may have a role in regulation of gene expression. Taken together, our data highlight novel mechanisms by which U-STAT3 binds to DNA and supports U-STAT3 function as a transcriptional activator and a chromatin/genomic organizer.

Article	Year
The role of the central atom in structure and reactivity of polyoxometalates with adjacent d-electron metal sites. computational and experimental studies of gamma-[(Xn+O4)RuIII2(OH)2(MFM)10O... The journal of physical chemistry. B\| PubMed ID: 16471516	2006
Mechanisms of unphosphorylated STAT3 transcription factor binding to DNA. The Journal of biological chemistry\| PubMed ID: 22378781	2012

Lyuba Khavrutskii

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