Effects of Distal Mutations on the Structure, Dynamics and Catalysis of Human Monoacylglycerol Lipase

An understanding of how conformational dynamics modulates function and catalysis of human monoacylglycerol lipase (hMGL), an important pharmaceutical target, can facilitate the development of novel ligands with potential therapeutic value. Here, we report the discovery and characterization of an allosteric, regulatory hMGL site comprised of residues Trp-289 and Leu-232 that reside over 18 Å away from the catalytic triad. These residues were identified as critical mediators of long-range communication and as important contributors to the integrity of the hMGL structure. Nonconservative replacements of Trp-289 or Leu-232 triggered concerted motions of structurally distinct regions with a significant conformational shift toward inactive states and dramatic loss in catalytic efficiency of the enzyme. Using a multimethod approach, we show that the dynamically relevant Trp-289 and Leu-232 residues serve as communication hubs within an allosteric protein network that controls signal propagation to the active site, and thus, regulates active-inactive interconversion of hMGL. Our findings provide new insights into the mechanism of allosteric regulation of lipase activity, in general, and may provide alternative drug design possibilities

ELECTRONIC SPECTRA OF THE HETEROISOTOPIC CH2DCH_{2} D AND CD2HCD_{2} H RADICALS

Author Institution: Chemical Kinetics and Thermodynamics Division, Chemical Science and Technology Laboratory, National Institute of Standards and TechnologyThe $3p ^{2}B_{1} \leftarrow \leftarrow \widetilde{X}^{2}B_{1}$ bands of $CH_{2}D$ and $CHD_{2}$ radicals were observed between 305 and 335 nm by mass resolved 2 + 1 resonance enhanced multiphoton ionization(REMP1) spectroscopy. Spectroscopic constants were found for the $3_{p} ^{2}B_{1}$ Rydberg state of the $CH_{2}D$ radical $(\nu_{00}=59940 cm^{-1}, \nu_{1} a_{1} CH_{2}$ stretch=$2995 cm^{-1}, \nu_{2} a_{1}$CD stretch=$2220 cm^{-1}, \nu_{4} b_{1} OPLA = 1260 cm^{-1}, \nu_{3} b_{2} CH_{2}$ asym stretch = $3055 cm^{-1}, \nu_{6} b_{2}$CD bend = $115 cm^{-1}$) and of the $CHD_{2}$ radical $(\nu_{00} = 59920 cm^{-1}, \nu_{1} a_{1}$CH stretch = $3040 cm^{-1}, \nu_{2} a_{1} CD_{2}$ stretch = $2150 cm^{-1}, \nu_{4} b_{1}$ OPLA = $1165 cm^{-1}, \nu_{6} b_{2}$CH bend =$1210 cm^{-1})$. Vibrational frequencies calculated by {ab initio} theory agree well with the experimental data

Synthetic Approach for Tunable, Size-Selective Formation of Monodisperse, Diphosphine-Protected Gold Nanoclusters

We report a new strategy that provides stringent control for the size and dispersity of ultrasmall nanoclusters through preparation of gold complex distributions formed from the precursor, AuClPPh₃ (PPh₃ = triphenylphosphine), and the L⁶ (L⁶ = 1,6-bis(diphenylphosphino) hexane) ligand prior to reduction with NaBH₄ in 1:1 methanol/chloroform solutions. Monodisperse nanoclusters of distinct nuclearity are obtained for specific ligand ratios; [L⁶]/[PPh₃] = 4 yields [Au₈L⁶₄]²⁺, [L⁶]/[PPh₃] = 0.4 yields [Au₉L⁶₄Cl]²⁺, and [L⁶]/[PPh₃] = 8 yields ligated Au₁₀ cores in the form of [Au₁₀L⁶₄]²⁺ and [Au₁₀L⁶₅]²⁺. Polyhedral skeletal electron pair theory accounts for the stability of [Au₉L⁶₄Cl]²⁺, which is the smallest closed-shell chlorinated cluster reported. Electrospray mass spectrometry and UV−vis spectra indicate that [Au₉L⁶₄Cl]²⁺ and [Au₁₀L⁶_<i>x</i>]²⁺ (<i>x</i> = 4, 5) result from reactions involving [Au₈L⁶₄]²⁺. Syntheses of small gold clusters containing chloride ligands open the possibility of constructing larger clusters via ligand exchange