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Fully anharmonic IR and Raman spectra of medium-size molecular systems: accuracy and interpretation.

ABSTRACT: Computation of full infrared (IR) and Raman spectra (including absolute intensities and transition energies) for medium- and large-sized molecular systems beyond the harmonic approximation is one of the most interesting challenges of contemporary computational chemistry. Contrary to common beliefs, low-order perturbation theory is able to deliver results of high accuracy (actually often better than those issuing from current direct dynamics approaches) provided that anharmonic resonances are properly managed. This perspective sketches the recent developments in our research group toward the development of a robust and user-friendly virtual spectrometer rooted in second-order vibrational perturbation theory (VPT2) and usable also by non-specialists essentially as a black-box procedure. Several examples are explicitly worked out in order to illustrate the features of our computational tool together with the most important ongoing developments.

SUBMITTER: Barone V

PROVIDER: S-EPMC4604664 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Fully anharmonic IR and Raman spectra of medium-size molecular systems: accuracy and interpretation.

Barone Vincenzo V Biczysko Malgorzata M Bloino Julien J

Physical chemistry chemical physics : PCCP 20140201 5

Computation of full infrared (IR) and Raman spectra (including absolute intensities and transition energies) for medium- and large-sized molecular systems beyond the harmonic approximation is one of the most interesting challenges of contemporary computational chemistry. Contrary to common beliefs, low-order perturbation theory is able to deliver results of high accuracy (actually often better than those issuing from current direct dynamics approaches) provided that anharmonic resonances are pro ...[more]

PMID: 24346191

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Project description:Mammalian target of rapamycin (mTOR) is involved in insulin resistance (IR) and diabetic retinopathy. In retinal pigment epithelial (RPE) cells, insulin activates the mTOR pathway, inducing hypoxia-inducible factor-1? (HIF-1?) and HIF-dependent transcription in serum-free minimum essential medium Eagle (MEM). Serendipitously, we found that insulin failed to induce the HIF-1?-dependent response, when RPE cells were cultured in Dulbecco's modification of Eagle's medium (DMEM). Whereas concentration of glucose in MEM corresponds to normal glucose levels in blood (5.5 mM), its concentration in DMEM corresponds to severe diabetic hyperglycemia (25 mM). Addition of glucose to MEM also caused IR. Glucose-mediated IR was characterized by basal activation of mTORC1 and its poor inducibility by insulin. Basal levels of phosphorylated S6 kinase (S6K), S6 and insulin receptor substrate 1 (IRS1) S635/639 were high, whereas their inducibilities were decreased. Insulin-induced Akt phosphorylation was decreased and restored by rapamycin and an inhibitor of S6K. IR was associated with de-phosphorylation of IRS1 at S1011, which was reversed by rapamycin. Both short (16-40 h) and chronic (2 weeks) treatment with rapamycin reversed IR. Furthermore, rapamycin did not impair Akt activation in RPE cells cultured in normoglycemic media. In contrast, Torin 1 blocked Akt activation by insulin. We conclude that by activating mTOR/S6K glucose causes feedback IR, preventable by rapamycin. Rapamycin does not cause IR in RPE cells regardless of the duration of treatment. We confirmed that rapamycin also did not impair phosphorylation of Akt at T308 and S473 in normal myoblast C2C12 cells. Our work provides insights in glucose-induced IR and suggests therapeutic approaches to treat patients with IR and severe hyperglycemia and to prevent diabetic complications such as retinopathy. Also our results prompt to reconsider physiological relevance of numerous data and paradigms on IR given that most cell lines are cultured with grossly super-physiological levels of glucose.

Dataset Information

Fully anharmonic IR and Raman spectra of medium-size molecular systems: accuracy and interpretation.

Publications

Fully anharmonic IR and Raman spectra of medium-size molecular systems: accuracy and interpretation.

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