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- Challis, B G, et al.
(författare)
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Mice lacking pro-opiomelanocortin are sensitive to high-fat feeding but respond normally to the acute anorectic effects of peptide-YY(3-36).
- 2004
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 101:13, s. 4695-700
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Tidskriftsartikel (refereegranskat)abstract
- Inactivating mutations of the pro-opiomelanocortin (POMC) gene in both mice and humans leads to hyperphagia and obesity. To further examine the mechanisms whereby POMC-deficiency leads to disordered energy homeostasis, we have generated mice lacking all POMC-derived peptides. Consistent with a previously reported model, Pomc(-/-) mice were obese and hyperphagic. They also showed reduced resting oxygen consumption associated with lowered serum levels of thyroxine. Hypothalami from Pomc(-/-) mice showed markedly increased expression of melanin-concentrating hormone mRNA in the lateral hypothalamus, but expression of neuropeptide Y mRNA in the arcuate nucleus was not altered. Provision of a 45% fat diet increased energy intake and body weight in both Pomc(-/-) and Pomc(+/-) mice. The effects of leptin on food intake and body weight were blunted in obese Pomc(-/-) mice whereas nonobese Pomc(-/-) mice were sensitive to leptin. Surprisingly, we found that Pomc(-/-) mice maintained their acute anorectic response to peptide-YY(3-36) (PYY(3-36)). However, 7 days of PYY(3-36) administration had no effect on cumulative food intake or body weight in wild-type or Pomc(-/-) mice. Thus, POMC peptides seem to be necessary for the normal response of energy balance to high-fat feeding, but not for the acute anorectic effect of PYY(3-36) or full effects of leptin on feeding. The finding that the loss of only one copy of the Pomc gene is sufficient to render mice susceptible to the effects of high fat feeding emphasizes the potential importance of this locus as a site for gene-environment interactions predisposing to obesity.
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- Adams, Samuel J., et al.
(författare)
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Surfactant-Enhanced Luminescence Lifetime for Biomolecular Detection on Luminescent Gold Surfaces Decorated with Transition Metal Complexes
- 2018
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Ingår i: ChemistrySelect. - 2365-6549. ; 3, s. 3251-3257
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Tidskriftsartikel (refereegranskat)abstract
- In the development of sensors based on multimodal detection, luminescent probes are attractive for providing a sensitive signal read-out, based either on intensity, wavelength shift or luminescence lifetime. The implicit simplicity of the devices that can be created is dependent of the judicious design of the multimodal probe. We have used transition metal probes which offer combined versatility due to their electroactive and photoluminescent properties, as well as their sensitivity to local environment. We report the influence of surfactant upon the formation of luminescent surfaces with metal complexes based on ruthenium(II), iridium(III) and osmium(II) bearing surface active groups. The results reveal an enhancement of the luminescence lifetime when a mixed monolayer with surfactant is formed. Characteristically, the luminescence lifetime of the ruthenium tris-bipyridyl complex attached to the gold surface increases from 210 ns to 765 ns in the presence of a fluorinated surfactant. The luminescence signal of the modified gold surfaces is also responsive to bovine serum albumin and fetal bovine serum adsorption, demonstrating interaction of the protein with the metal complex in the presence of the surfactant. The biomolecular interaction with the functionalised surfaces is also evidenced by surface plasmon resonance response.
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- Nemec, Hynek, et al.
(författare)
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Influence of the Electron-Cation Interaction on Electron Mobility in Dye-Sensitized ZnO and TiO2 Nanocrystals: A Study Using Ultrafast Terahertz Spectroscopy
- 2010
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Ingår i: Physical Review Letters. - 1079-7114. ; 104:19
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Tidskriftsartikel (refereegranskat)abstract
- Charge transport and recombination in nanostructured semiconductors are poorly understood key processes in dye-sensitized solar cells. We have employed time-resolved spectroscopies in the terahertz and visible spectral regions supplemented with Monte Carlo simulations to obtain unique information on these processes. Our results show that charge transport in the active solar cell material can be very different from that in nonsensitized semiconductors, due to strong electrostatic interaction between injected electrons and dye cations at the surface of the semiconductor nanoparticle. For ZnO, this leads to formation of an electron-cation complex which causes fast charge recombination and dramatically decreases the electron mobility even after the dissociation of the complex. Sensitized TiO2 does not suffer from this problem due to its high permittivity efficiently screening the charges.
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