Domain Analysis and Motif Matcher (DAMM): A Program to Predict Selectivity Determinants in Monosiga brevicollis PDZ Domains Using Human PDZ Data

Choanoflagellates are single-celled eukaryotes with complex signaling pathways. They are considered the closest non-metazoan ancestors to mammals and other metazoans and form multicellular-like states called rosettes. The choanoflagellate Monosiga brevicollis contains over 150 PDZ domains, an important peptide-binding domain in all three domains of life (Archaea, Bacteria, and Eukarya). Therefore, an understanding of PDZ domain signaling pathways in choanoflagellates may provide insight into the origins of multicellularity. PDZ domains recognize the C-terminus of target proteins and regulate signaling and trafficking pathways, as well as cellular adhesion. Here, we developed a computational software suite, Domain Analysis and Motif Matcher (DAMM), that analyzes peptide-binding cleft sequence identity as compared with human PDZ domains and that can be used in combination with literature searches of known human PDZ-interacting sequences to predict target specificity in choanoflagellate PDZ domains. We used this program, protein biochemistry, fluorescence polarization, and structural analyses to characterize the specificity of A9UPE9_MONBE, a M. brevicollis PDZ domain-containing protein with no homology to any metazoan protein, finding that its PDZ domain is most similar to those of the DLG family. We then identified two endogenous sequences that bind A9UPE9 PDZ with <100 μM affinity, a value commonly considered the threshold for cellular PDZ–peptide interactions. Taken together, this approach can be used to predict cellular targets of previously uncharacterized PDZ domains in choanoflagellates and other organisms. Our data contribute to investigations into choanoflagellate signaling and how it informs metazoan evolution.     

Structure and Magnetization Dynamics of Dy−Fe and Dy−Ru Bonded Complexes

We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy³⁺) and either a first‐row (Fe) or a second‐row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp₂^2? (PyCp₂^2?=[2,6‐(CH₂C₅H₃)₂C₅H₃N]^2?) facilitates the isolation and characterization of PyCp₂Dy?FeCp(CO)₂ ( 1 ; d(Dy–Fe)=2.884(2) Å) and PyCp₂Dy?RuCp(CO)₂ ( 2 ; d(Dy–Ru)=2.9508(5) Å). Computational and spectroscopic studies suggest strong TM→Dy bonding interactions. Both complexes exhibit field‐induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy?Fe to Dy?Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin–phonon coupling contributions to magnetic relaxation.     

Microbial control of hydrogen sulfide production in a porous medium

Applied Biochemistry and Biotechnology - The ability of a sulfide- and glutaraldehyde-tolerant strain ofThiobacillus denitrificans (strain F) to control sulfide production in an experimental system...     

High resolution Fourier transform infrared spectroscopy using a high temperature argon arc source

Application of a high temperature wall-stabilized argon arc source (HTAAS) for high resolution near- and mid-infrared Fourier transform infrared spectroscopy (FTIR) has been investigated. Spectra of N₂O, NH₃ and the complex OC-HCl were recorded at maximum apodized instrumental resolution (0.004 cm⁻¹). The signal to noise (S/N) ratio of these molecular absorption transitions were compared with corresponding spectra recorded using a 1520(30) K globar source. At 7.6 μm, recorded ¹⁴N₂ ¹⁶O transitions are consistent with a HTAAS at approximately 10,000 K and an enhancement of 12.6 in recorded S/N ratios with respect to the latter globar source. Such results demonstrate a significantly enhanced performance for specific FTIR applications such as high resolution static gas phase spectroscopy and molecular spectroscopy in supersonic jet expansions, and potentially for infrared microscopy.     

Copolymerization of butadiene and styrene by initiation with alkyllithium and alkali metal tert-butoxides

Combinations of the various alkali metal tert-butoxides with organolithium initiators give homogeneous copolymers of butadiene and styrene. The unprecedented flexibility of this initiator system allowed preparation of random copolymers with various amounts of vinyl unsaturation and various degrees of randomness. The butyllithium–potassium tert-butoxide initiator system was more efficient than phenylpotassium.     

Alkyllithium and alkali metal tert-butoxide as polymerization initiator

We have shown that the presence of other alkali metal alkoxides in the alkyllithium-initiated polymerization drastically increases the rate of polymerization and vinyl unsaturation in polybutadiene. Mechanistically, the propagating center is the dynamic equilibriums between carbon–metal bonds and oxygen–metal bonds. With potassium, rubidium, and cesium salts it reaches a limiting anionic behavior.