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41.
42.
Pooventhiran T. Bhattacharyya Utsab Rao D. Jagadeeswara Chandramohan Vivek Karunakar Prashantha Irfan Ahmad Mary Y. Sheena Thomas Renjth 《Structural chemistry》2020,31(6):2475-2485
43.
Hodkinson JP Jahn TR Radford SE Ashcroft AE 《Journal of the American Society for Mass Spectrometry》2009,20(2):278-286
The light chain of the major histocompatibility complex class 1 (MHC-1), the protein β
2-microglobulin (β
2m), has amyloidogenic properties that arise only upon its dissociation from the MHC-1. Here hydrogen/deuterium exchange electrospray
ionization mass spectrometry (HDX-ESI-MS) has been used to compare the solution dynamics of β
2m in its MHC-1 bound state compared with those of β
2m as a free monomer. The capability of tandem mass spectrometry to dissociate the MHC-1 into its individual constituents in
the gas phase following deuterium incorporation in solution has permitted the direct observation of the exchange properties
of MHC-1 bound β
2m for the first time. The HDX-ESI-MS data show clearly that the H→D exchange of MHC-1 bound β
2m follows EX2 kinetics and that about 20 protons remain protected from exchange after 17 days. Free from the MHC-1, monomeric
β
2m exhibits significantly different HDX behavior, which encompasses both EX1 and EX2 kinetics. The EX2 kinetics indicate a
tenfold increase in the rate of exchange compared with MHC-1 bound β
2m, with just 10 protons remaining protected from EX2 exchange and therefore exchanging only via the EX1 mechanism. The EX1
kinetics observed for unbound β
2m are consistent with unfolding of its exchange-protected core with a t1/2 of 68 min (pH 7, 37° C). Thus, upon dissociation from the stabilizing influence of the MHC-1, free β
2m becomes highly dynamic and undergoes unfolding transitions that result in an aggregation-competent protein. 相似文献
44.
Replacement of NH3 by a planar amine L to give trans-[PtCl2(L)(L')] (L = NH3, L'= pyridine or substituted pyridine, quinoline, isoquinoline, thiazole; L = L'= pyridine, thiazole), greatly enhances the cytotoxicity of the transplatinum geometry. The "parent" compound trans-[PtCl2(NH3)2] is therapeutically inactive. Modification of the ligands to an [N2O2] donor set, where O represents an acetate leaving group, enhances the aqueous solubility while retaining the cytotoxicity of the parent chloride compounds. The effect of two mutual trans leaving groups with weak trans influence is to impart remarkable chemical stability on the structure. This strategy is analogous to the use of the inert dicarboxylate leaving groups in the clinical compounds carboplatin and oxaliplatin. In this paper, systematic modification of the steric effects of carrier pyridine groups and, especially, carboxylate leaving groups in trans-[Pt(O2CR)2(NH3)(pyr)] is shown to modulate aqueous solubility and hydrolysis to the activated aqua species. The results presented here demonstrate the utility of the "carboxylate strategy" in "fine-tuning" the chemical and pharmacokinetic properties in the design of clinically relevant transplatinum complexes. 相似文献
45.
C. Yohannan Panicker Hema Tresa Varghese L. Ushakumari Y. Sheena Mary Jyotirmoy Sarkar Joydeep Chowdhury 《Journal of Raman spectroscopy : JRS》2010,41(9):944-951
IR, Raman and surface‐enhanced Raman scattering (SERS) spectra of sulfanilic acid sodium salt (SANA) were recorded and analysed. The vibrational wavenumbers were computed by the density functional theory method using the B3LYP/6–31G* basis and found to be in good agreement with the experimental values. The effect of concentration and pH dependence on the SERS intensity of the molecule was also studied. The molecular plane assumes a tilted orientation with respect to the silver surface. The observed changes of the relative intensities of some enhanced bands and the presence of in‐plane and out‐of‐plane modes of the phenyl ring suggest that the molecule assumes a more tilted orientation upon lowering the concentration of the adsorbate. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
46.
Enzyme‐Mediated Site‐Specific Bioconjugation of Metal Complexes to Proteins: Sortase‐Mediated Coupling of Copper‐64 to a Single‐Chain Antibody
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Dr. Brett M. Paterson Dr. Karen Alt Charmaine M. Jeffery Prof. Roger I. Price Shweta Jagdale Dr. Sheena Rigby Dr. Charlotte C. Williams Prof. Karlheinz Peter Prof. Christoph E. Hagemeyer Assoc. Prof. Paul S. Donnelly 《Angewandte Chemie (International ed. in English)》2014,53(24):6115-6119
The enzyme‐mediated site‐specific bioconjugation of a radioactive metal complex to a single‐chain antibody using the transpeptidase sortase A is reported. Cage amine sarcophagine ligands that were designed to function as substrates for the sortase A mediated bioconjugation to antibodies were synthesized and enzymatically conjugated to a single‐chain variable fragment. The antibody fragment scFvanti‐LIBS targets ligand‐induced binding sites (LIBS) on the glycoprotein receptor GPIIb/IIIa, which is present on activated platelets. The immunoconjugates were radiolabeled with the positron‐emitting isotope 64Cu. The new radiolabeled conjugates were shown to bind selectively to activated platelets. The diagnostic potential of the most promising conjugate was demonstrated in an in vivo model of carotid artery thrombosis using positron emission tomography. This approach gives homogeneous products through site‐specific enzyme‐mediated conjugation and should be broadly applicable to other metal complexes and proteins. 相似文献
47.
Leney AC Phan G Allen W Verger D Waksman G Radford SE Ashcroft AE 《Journal of the American Society for Mass Spectrometry》2011,22(7):1214-1223
P pili are hair-like adhesive structures that are assembled on the outer membrane (OM) of uropathogenic Escherichia coli by the chaperone-usher pathway. In this pathway, chaperone-subunit complexes are formed in the periplasm and targeted to
an OM assembly platform, the usher. Pilus subunits display a large groove caused by a missing β-strand which, in the chaperone-subunit
complex, is provided by the chaperone. At the usher, pilus subunits are assembled in a mechanism termed “donor-strand exchange
(DSE)” whereby the β-strand provided by the chaperone is exchanged by the incoming subunit’s N-terminal extension (Nte). This
occurs in a zip-in-zip-out fashion, starting with a defined residue, P5, in the Nte inserting into a defined site in the groove,
the P5 pocket. Here, electrospray ionization-mass spectrometry (ESI-MS) has been used to measure DSE rates in vitro. Second
order rate constants between the chaperone-subunit complex and a range of Nte peptides substituted at different residues confirmed
the importance of the P5 residue of the Nte in determining the rate of DSE. In addition, residues either side of the P5 residue
(P5 + 1 and P5 – 1), the side-chains of which are directed away from the subunit groove, also modulate the rates of DSE, most
likely by aiding the docking of the Nte into the P5 pocket on the accepting subunit prior to DSE. The ESI-MS approach developed
is applicable to the measurement of rates of DSE in pilus biogenesis in general and demonstrates the scope of ESI-MS in determining
biomolecular processes in molecular detail. 相似文献
48.
Pfingst BE Colesa DJ Hembrador S Kang SY Middlebrooks JC Raphael Y Su GL 《The Journal of the Acoustical Society of America》2011,130(6):3954-3968
Perception of electrical stimuli varies widely across users of cochlear implants and across stimulation sites in individual users. It is commonly assumed that the ability of subjects to detect and discriminate electrical signals is dependent, in part, on conditions in the implanted cochlea, but evidence supporting that hypothesis is sparse. The objective of this study was to define specific relationships between the survival of tissues near the implanted electrodes and the functional responses to electrical stimulation of those electrodes. Psychophysical and neurophysiological procedures were used to assess stimulus detection as a function of pulse rate under the various degrees of cochlear pathology. Cochlear morphology, assessed post-mortem, ranged from near-normal numbers of hair cells, peripheral processes and spiral ganglion cells, to complete absence of hair cells and peripheral processes and small numbers of surviving spiral ganglion cells. The psychophysical and neurophysiological studies indicated that slopes and levels of the threshold versus pulse rate functions reflected multipulse integration throughout the 200 ms pulse train with an additional contribution of interactions between adjacent pulses at high pulse rates. The amount of multipulse integration was correlated with the health of the implanted cochlea with implications for perception of more complex prosthetic stimuli. 相似文献
49.
50.
Sheena A. Hindocha 《Journal of solid state chemistry》2009,182(5):1070-6908
Layered lanthanide hydroxynitrate anion exchange host lattices have been prepared via a room temperature precipitation synthesis. These materials have the composition Ln2(OH)5NO3·H2O and are formed for Y and the lanthanides from Eu to Er and as such include the first Eu containing nitrate anion exchange host lattice. The interlayer separation of these materials, approximately 8.5 Å, is lower than in the related phases Ln2(OH)5NO3·1.5H2O which have a corresponding value of 9.1 Å and is consistent with the reduction in the co-intercalated water content of these materials. These new intercalation hosts have been shown to undergo facile anion exchange reactions with a wide range of organic carboxylate and sulfonate anions. These reactions produce phases with up to three times the interlayer separation of the host lattice demonstrating the flexibility of these materials. 相似文献