Long-chain alkyltrichlorosilanes, Cl3Si(CH2)"R, adsorb from solution onto silicon-silicon dioxide (Si/SiOŝ ubstrates and form ordered alkylsiloxane monolayer films. These films were characterized by wettability, ellipsometry, and XPS. Except for very short chains (n = 0, 1, 2), the wetting of these monolayers was approximately independent of chain length. The presence of small amounts of water was necessary for the formation of these films. The alkylsiloxane monolayers were stable in common organic solvents, water, and acid but were destroyed by prolonged exposure to base. Simple reactions on vinyl-terminated monolayers generated alcohol-, carboxylic acid-, and bromine-terminated films whose contact angles were lower than the starting monolayers but whose lengths were largely unchanged. Measurements of the contact angle of acid-terminated interfaces as a function of pH indicated that ionization of the surface-immobilized acids required stronger base than does ionization of soluble carboxylic acids. Monolayers containing mixtures of methyl and carboxyl functionalities exhibited wetting properties that mirrored the composition of the interface.Because the organosilicon-derived monolayers are physically robust, they are widely used in technology,24,25

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Protein arginine methyltransferases (PRMTs) play important roles in several cellular processes, including signaling, gene regulation, and transport of proteins and nucleic acids, to impact growth, differentiation, proliferation, and development. PRMT5 symmetrically di-methylates the two-terminal ω-guanidino nitrogens of arginine residues on substrate proteins. PRMT5 acts as part of a multimeric complex in concert with a variety of partner proteins that regulate its function and specificity. A core component of these complexes is the WD40 protein MEP50/WDR77/p44, which mediates interactions with binding partners and substrates. We have determined the crystal structure of human PRMT5 in complex with MEP50 (methylosome protein 50), bound to an S-adenosylmethionine analog and a peptide substrate derived from histone H4. The structure of the surprising hetero-octameric complex reveals the close interaction between the seven-bladed β-propeller MEP50 and the N-terminal domain of PRMT5, and delineates the structural elements of substrate recognition.epigenetics | protein-protein complex | A9145C P osttranslational methylation of lysine and arginine residues by protein lysine methyltransferases and protein arginine methyltransferases (PRMTs) alters the activity and interactions of substrate proteins, with crucial consequences to diverse cellular functions (1-3). Histone methylation is an epigenetic mark that plays a vital role in normal cell function, and whose dysregulation is associated with several diseases (4).The PRMT family of methyltransferases belongs to the largest class (class I) of S-adenosylmethionine (AdoMet)-dependent methyltransferase enzymes, responsible for the transfer of a methyl group from AdoMet to the arginine side-chains of histones and other proteins. PRMTs are further subdivided into type I, type II, type III, and type IV enzymes based on their patterns of arginine methylation. Eleven human PRMTs have been identified to date (5), and they all methylate the terminal guanidino nitrogen atoms of arginine residues. Type I PRMT enzymes (PRMT1, -2, -3, -4, -6, and -8) generate ω-NG-monomethyl and ω-NG,NG-asymmetric di-methyl arginines, whereas PRMT5 is a type II PRMT that catalyzes the formation of ω-NG-monomethyl and ω-NG,N′G-symmetric di-methyl arginine residues. PRMT7 was initially thought to have type II activity, but recent evidence suggests that it may be a type III enzyme that is only able to monomethylate substrates to form ω-NG-monomethyl arginine (6). A type IV enzyme that catalyses the formation of δ-N-methyl arginine has been identified in yeast (7). All PRMTs share the highly conserved methyltransferase catalytic domain, and several PRMTs contain additional domains that modulate their activity and specificity. PRMT2, PRMT3, and PRMT9 contain SH3, zinc finger, and TRP2 domains, respectively, and PRMT5 contains a largely uncharacterized N-terminal region.In contrast to type I PRMTs, PRMT5 functions as part of various high molecular weight protein complexes that invariably contain the WD-repe...

Axe. 1990. X-ray specular reflection studies of silicon coated by organic monolayers (alkylsiloxanes). Physical Review B 41(2): 1111-1128.