Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Journal Of The American Chemical Society  (131)
Type of Medium
Language
Year
Journal
  • 1
    Language: English
    In: Journal of the American Chemical Society, 19 January 2011, Vol.133(2), pp.167-9
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Journal of the American Chemical Society, 03 April 2013, Vol.135(13), pp.5062-7
    Description: We investigated salt interactions with butyramide as a simple mimic of cation interactions with protein backbones. The experiments were performed in aqueous metal chloride solutions using two spectroscopic techniques. In the first, which provided information about contact pair formation, the response of the amide I band to the nature and concentration of salt was monitored in bulk aqueous solutions via attenuated total reflection Fourier transform infrared spectroscopy. It was found that molar concentrations of well-hydrated metal cations (Ca(2+), Mg(2+), Li(+)) led to the rise of a peak assigned to metal cation-bound amides (1645 cm(-1)) and a decrease in the peak associated with purely water-bound amides (1620 cm(-1)). In a complementary set of experiments, the effect of cation identity and concentration was investigated at the air/butyramide/water interface via vibrational sum frequency spectroscopy. In these studies, metal ion-amide binding led to the ordering of the adjacent water layer. Such experiments were sensitive to the interfacial partitioning of cations in either a contact pair with the amide or as a solvent separated pair. In both experiments, the ordering of the interactions of the cations was: Ca(2+) 〉 Mg(2+) 〉 Li(+) 〉 Na(+) ≈ K(+). This is a direct cationic Hofmeister series. Even for Ca(2+), however, the apparent equilibrium dissociation constant of the cation with the amide carbonyl oxygen was no tighter than ∼8.5 M. For Na(+) and K(+), no evidence was found for any binding. As such, the interactions of metal cations with amides are far weaker than the analogous binding of weakly hydrated anions.
    Keywords: Amides -- Chemistry ; Water -- Chemistry
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Journal of the American Chemical Society, 20 June 2012, Vol.134(24), pp.10039-46
    Description: The specific binding sites of Hofmeister ions with an uncharged 600-residue elastin-like polypeptide, (VPGVG)(120), were elucidated using a combination of NMR and thermodynamic measurements along with molecular dynamics simulations. It was found that the large soft anions such as SCN(-) and I(-) interact with the polypeptide backbone via a hybrid binding site that consists of the amide nitrogen and the adjacent α-carbon. The hydrocarbon groups at these sites bear a slight positive charge, which enhances anion binding without disrupting specific hydrogen bonds to water molecules. The hydrophobic side chains do not contribute significantly to anion binding or the corresponding salting-in behavior of the biopolymer. Cl(-) binds far more weakly to the amide nitrogen/α-carbon binding site, while SO(4)(2-) is repelled from both the backbone and hydrophobic side chains of the polypeptide. The Na(+) counterions are also repelled from the polypeptide. The identification of these molecular-level binding sites provides new insights into the mechanism of peptide-anion interactions.
    Keywords: Ions -- Chemistry ; Peptides -- Chemistry
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Journal of the American Chemical Society, 09 May 2012, Vol.134(18), pp.7773-9
    Description: Phosphatidylserine (PS) embedded within supported lipid bilayers was found to bind Cu(2+) from solution with extraordinarily high affinity. In fact, the equilibrium dissociation constant was in the femtomolar range. The resulting complex formed in a 1:2 Cu(2+)-to-PS ratio and quenches a broad spectrum of lipid-bound fluorophores in a reversible and pH-dependent fashion. At acidic pH values, the fluorophores were almost completely unquenched, while at basic pH values significant quenching (85-90%) was observed. The pH at which the transition occurred was dependent on the PS concentration and ranged from approximately pH 5 to 8. The quenching kinetics was slow at low Cu(2+) concentrations and basic pH values (up to several hours), while the unquenching reaction was orders of magnitude more rapid upon lowering the pH. This was consistent with diffusion-limited complex formation at basic pH but rapid dissociation under acidic conditions. The tight binding of Cu(2+) to PS may have physiological consequences under certain circumstances.
    Keywords: Copper -- Metabolism ; Lipid Bilayers -- Metabolism ; Phosphatidylserines -- Metabolism
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Journal of the American Chemical Society, 06 April 2016, Vol.138(13), pp.4334-7
    Description: For the first time, nonclassical hydrogen (H)-bonding involving a B-H···π interaction is described utilizing both quantum chemical predictions and experimental realization. In the gas phase, a B-H···π H-bond is observed in either B2H6···benzene (ΔE = -5.07 kcal/mol) or carborane···benzene (ΔE = -3.94 kcal/mol) complex at reduced temperatures. Ir-dimercapto-carborane complexes [Cp*Ir(S2C2B10H10)] are designed to react with phosphines PR3 (R = C6H4X, X = H, F, OMe) to give [Cp*Ir(PR3)S2C2B10H10] for an investigation of B-H···π interactions at ambient temperatures. X-ray diffraction studies reveal that the interaction between the carborane BH bonds and the phosphine aryl substituents involves a BH···π H-bond (H···π distance: 2.40-2.76 Å). (1)H NMR experiments reveal that B-H···π interactions exist in solution according to measured (1)H{(11)B} signals at ambient temperatures in the range 0.0 ≤ δ ≤ 0.3 ppm. These are high-field shifted by more than 1.5 ppm relative to the (1)H{(11)B} signals obtained for the PMe3 analog without B-H···π bonding. Quantum chemical calculations suggest that the interaction is electrostatic and the local (B)H···ring stretching force constant is as large as the H-bond stretching force constant in the water dimer.
    Keywords: Chemistry;
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Journal of the American Chemical Society, 26 September 2012, Vol.134(38), pp.15832-9
    Description: Single-particle tracking experiments were carried out with gold nanoparticle-labeled solid supported lipid bilayers (SLBs) containing increasing concentrations of ganglioside (GM(1)). The negatively charged nanoparticles electrostatically associate with a small percentage of positively charged lipids (ethyl phosphatidylcholine) in the bilayers. The samples containing no GM(1) show random diffusion in 92% of the particles examined with a diffusion constant of 4.3(±4.5) × 10(-9) cm(2)/s. In contrast, samples containing 14% GM(1) showed a mixture of particles displaying both random and confined diffusion, with the majority of particles, 62%, showing confined diffusion. Control experiments support the notion that the nanoparticles are not associating with the GM(1) moieties but instead most likely confined to regions in between the GM(1) clusters. Analysis of the root-mean-squared displacement plots for all of the data reveals decreasing trends in the confined diffusion constant and diameter of the confining region versus increasing GM(1) concentration. In addition, a linearly decreasing trend is observed for the percentage of randomly diffusing particles versus GM(1) concentration, which offers a simple, direct way to measure the percolation threshold for this system, which has not previously been measured. The percolation threshold is found to be 22% GM(1) and the confining diameter at the percolation threshold only ∼50 nm.
    Keywords: Lipid Bilayers ; Nanoparticles ; Gangliosides -- Chemistry
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: Journal of the American Chemical Society, June 24, 2015, Vol.137(24), pp.7785-7792
    Description: The article describes the measurement of the apparent equilibrium dissociation constant, [K.sub.Dapp], between [Cu.sup.2+] and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), a negatively charged phospholipid, as a function of PS concentrations in supported lipid bilayers (SLBs). The results revealed an enhancement in [K.sub.Dapp] for [Cu.sup.2+] binding to PS-containing SLBs by a factor of 17?000 from 110 nM to 6.4 pM as the PS density in the membrane was increased from 1.0 to 20 mol %. The higher concentration of [Cu.sup.2+] within the double layer above the membrane was largely responsible for the increased binding affinity.
    Keywords: Phosphatidylserines – Chemical Properties ; Copper (Metal) – Chemical Properties
    ISSN: 0002-7863
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Journal of the American Chemical Society, 24 June 2015, Vol.137(24), pp.7785-92
    Description: Herein, the apparent equilibrium dissociation constant, K(Dapp), between Cu(2+) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), a negatively charged phospholipid, was measured as a function of PS concentrations in supported lipid bilayers (SLBs). The results indicated that K(Dapp) for Cu(2+) binding to PS-containing SLBs was enhanced by a factor of 17,000 from 110 nM to 6.4 pM as the PS density in the membrane was increased from 1.0 to 20 mol %. Although Cu(2+) bound bivalently to POPS at higher PS concentrations, this was not the dominant factor in increasing the binding affinity. Rather, the higher concentration of Cu(2+) within the double layer above the membrane was largely responsible for the tightening. Unlike the binding of other divalent metal ions such as Ca(2+) and Mg(2+) to PS, Cu(2+) binding does not alter the net negative charge on the membrane as the Cu(PS)2 complex forms. As such, the Cu(2+) concentration within the double layer region was greatly amplified relative to its concentration in bulk solution as the PS density was increased. This created a far larger enhancement to the apparent binding affinity than is observed by standard multivalent effects. These findings should help provide an understanding on the extent of Cu(2+)-PS binding in cell membranes, which may be relevant to biological processes such as amyloid-β peptide toxicity and lipid oxidation.
    Keywords: Copper -- Metabolism ; Lipid Bilayers -- Metabolism ; Phosphatidylserines -- Metabolism
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Journal of the American Chemical Society, Feb 10, 2016, Vol.138(5), pp.1584-1590
    Description: The article demonstrates that [Cu.sup.2+] binds bivalently to phosphatidylethanolamine (PE), the second most abundant lipid in mammalian cell. It is possible to monitor the oxidation of double bonds in PE-containing bilayers in the presence of [Cu.sup.2+]. Remarkably, the oxidation rate is 8.2 times faster at pH 7.4 for bilayers containing 70 mol % PE than for pure phosphatidylcholine (PC) bilayers upon exposure of both to 70 muM [Cu.sup.2+] and 10 mM hydrogen peroxide.
    Keywords: Copper Compounds – Chemical Properties ; Oxidation-Reduction Reactions – Research ; Lipid Membranes – Research ; Phosphatidylethanolamines – Chemical Properties
    ISSN: 0002-7863
    Source: Cengage Learning, Inc.
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Journal of the American Chemical Society, 10 February 2016, Vol.138(5), pp.1584-90
    Description: Herein, we demonstrate that Cu(2+) binds bivalently to phosphatidylethanolamine (PE), the second most abundant lipid in mammalian cells. The apparent equilibrium dissociation constant, K(DApp), for the Cu(2+)-PE complex at physiological pH is approximately 2 μM and is insensitive to the concentration of PE in the membrane. By contrast, at pH 10.0, where PE lipids bear a negative charge, K(DApp) decreases with increasing PE content and has a value of 150 nM for bilayers containing 70 mol % PE. The oxidation of double bonds in PE-containing bilayers can be monitored in the presence of Cu(2+). Strikingly, it was found that the oxidation rate is 8.2 times faster at pH 7.4 for bilayers containing 70 mol % PE than for pure phosphatidylcholine (PC) bilayers upon exposure of both to 70 μM Cu(2+) and 10 mM hydrogen peroxide. The rate of oxidation increases linearly with the PE content in the membrane. These results may help explain the high level of lipid oxidation in PE-containing membranes for neurodegenerative diseases and autism where the Cu(2+) concentration in the body is abnormally high.
    Keywords: Lipid Bilayers ; Copper -- Chemistry ; Phosphatidylethanolamines -- Chemistry
    ISSN: 00027863
    E-ISSN: 1520-5126
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages