- Kinetics of Volatilization in Rapid Heating Mass Spectroscopy: Activation Energies for Some Hydrogen-Bonding Species
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Activation energies and characteristic temperatures for the volatilization of several hydrogen-bonding compounds with mild to rapid heating mass spectroscopy techniques are reported.A homologous series of N-acetyl(L-alanine)n methyl esters, di- through pentaalanine, show a reguler increase in activation energy of 7-9 kcal/mol per alanine residue as studied by single-ion-impact tandem mass spectroscopy.The rapid heating-chemical ionization mass spectroscopy of glycerol, meso- and pentaerythritol, D(+)-mannose, D(+)-glucose, sucrose, and maltose with ammonia and methane reagent gases gives activation energies for the production of protonated or cationized molecular ions which resemble experimental heats of vaporizaton for the polyalcohols and amount to ca. 4.4 kcal/mol per CHOH group in these compounds.Trends in these data, along with the production of fragment ions in the case of the disaccharides, are briefly discussed.
- Williams, Brian Wesley,Irsa, A. Peter,Zmora, Hagai,Beuhler, Robert J.
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- Metallopolymer-peptide hybrid materials: Synthesis and self-assembly of functional, polyferrocenylsilane-tetrapeptide conjugates
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Conjugates of poly(ferrocenyldimethylsilane) (PFDMS) with Ac-(GA) 2-OH, Ac-A4-OH, Ac-G4-OH and Ac-V 4-OH have been prepared by reaction of the tetrapeptide units with the amino-terminated metallopolymer. The number average degree of polymerisation (DPn) of the PFDMS was approximately 20 and comparable materials with shorter (DPn≈10) and/or amorphous chains have been prepared by the same procedure. Poly(ferrocenylethylmethylsilane) (PFEMS) was employed for the latter purpose. All conjugates were characterised by GPC, MALDI-TOF MS, NMR and IR spectroscopy. With the exception of Ac-V4-PFDMS 20, all materials exhibited some anti-parallel β-sheet structure in the solid state. The self-assembly of the conjugates was studied in toluene by DLS. The vast majority of the materials, irrespective of peptide sequence or chain crystallinity, afforded fibres consisting of a peptidic core surrounded by a PFS corona. These fibres were found in the form of cross-linked networks by TEM and AFM. The accessibility of the chemically reducing PFS corona has been demonstrated by the localised formation of silver nanoparticles on the surface of the fibres. Stemming the (pep)tide: Polyferrocenylsilane-tetrapeptide conjugates can self-assemble in toluene to afford fibrous networks. The functional metallopolymer, which forms the coronae of the core-shell structure, can then be employed for the patterning of silver nanoparticles (see scheme). Copyright
- Tangbunsuk, Siree,Whittell, George R.,Ryadnov, Maxim G.,Vandermeulen, Guido W. M.,Woolfson, Derek N.,Manners, Ian
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