Purpose Low molecular weight iron(III) complex-based contrast agents (IBCA) including trans-cyclohexane diamine tetraacetic acid [Fe(tCDTA)]? could serve as alternatives to gadolinium-based in MRI. In search for IBCA with enhanced properties, we synthesized derivatives of and compared their effects. Methods Trans-cyclohexane (tCDTA) was chemically modified 2 steps: first the monoanhydride gener...

The title compound, [Eu2(C7H5O2)6(C15H11N3)2(H2O)2]·2C7H6O2, is a co-crystalline compound containing a dinuclear Eu(III) coordination complex with inversion symmetry co-crystallized with benzoic acid in a 1:2 ratio. The Eu(3+) ions within the dimer are nine-coordinate, containing one tridentate terpyridine, one water, and four benzoate ions, two of which bridge the Eu(3+) ions. Of the four benz...

The ATP-dependent chromatin-remodeling complex SWR1 exchanges a variant histone H2A.Z/H2B dimer for a canonical H2A/H2B dimer at nucleosomes flanking histone-depleted regions, such as promoters. This localization of H2A.Z is conserved throughout eukaryotes. SWR1 is a 1 megadalton complex containing 14 different polypeptides, including the AAA+ ATPases Rvb1 and Rvb2. Using electron microscopy, w...

To cut DNA at their target sites, restriction enzymes assemble into different oligomeric structures. The Ecl18kI endonuclease in the crystal is arranged as a tetramer made of two dimers each bound to a DNA copy. However, free in solution Ecl18kI is a dimer. To find out whether the Ecl18kI dimer or tetramer represents the functionally important assembly, we generated mutants aimed at disrupting ...

The chemical modification of two new double-headed protease inhibitors from black-eyed peas, a trypsin-chymotrypsin inhibitor (BEPCI) and a trypsin inhibitor (BEPTI) with dansyl chloride was investigated under various conditions. The NH,-terminal serine of both BEPCI and BEPTI, the 4 lysyl residues of BEPCI, and 4 of the 5 lysyl residues of BEPTI, could not be dansylated in the absence of urea....

The interaction of proteins bound to sites widely separated on the genome is a recurrent motif in both prokaryotic and eukaryotic regulatory systems. Lac repressor mediates the formation of "DNA loops" by the simultaneous interaction of a single protein tetramer with two DNA-binding sites. The DNA-binding properties of a Lac repressor mutant (LacIadi) deficient in the association of protein dim...

Escherichia coli UvrD protein is a 3' to 5' SF1 helicase required for DNA repair as well as DNA replication of certain plasmids. We have shown previously that UvrD can self-associate to form dimers and tetramers in the absence of DNA, but that a UvrD dimer is required to form an active helicase-DNA complex in vitro. Here we have used pre-steady state, chemical quenched flow methods to examine t...

Complex U consists of orotate phosphoribosyltransferase (EC 2.4.2.10) and orotidineG’-phosphate decarboxylase (EC 4.1.1.23), the last two enzymes of the de nova pathway for UMP biosynthesis. Earlier studies had shown that orotate and magnesium 5-phosphoribosyl-1-pyrophosphate, substrates for the transferase, and orotidine 5’-monophosphate (OMP), the product of the transferase and also the subst...

Exposure of phosphatidylserine (PS) molecules on activated platelet membrane surface is a crucial event in blood coagulation. Binding of PS to specific sites on factor Xa (fXa) and factor Va (fVa) promotes their assembly into a complex that enhances proteolysis of prothrombin by approximately 10⁵. Recent studies demonstrate that both soluble PS and PS-containing model membranes promote formatio...

The human herpes simplex virus type 1 regulatory protein ICP4 binds DNA as a dimer and forms a single protein-DNA complex (A complex) with short DNA probes. ICP4 oligomerized in a DNA-dependent manner, forming two or more protein-DNA complexes with longer DNA fragments containing a single DNA binding site. When resolved electrophoretically, one or more low-mobility DNA-protein complexes follow ...