| 361. |
- Nordén, Bengt, 1945, et al.
(författare)
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X-POLARIZED AND Y-POLARIZED SPECTRA OF CHLOROPHYLL-A AND PHEOPHYTIN-A IN THE RED REGION - RESOLUTION ENHANCEMENT AND GAUSSIAN DECONVOLUTION
- 1992
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Ingår i: Australian Journal of Chemistry. - : CSIRO Publishing. - 1445-0038 .- 0004-9425. ; 45:10, s. 1559-1570
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Tidskriftsartikel (refereegranskat)abstract
- The red region of the X- and Y-polarized spectra obtained from the measurement of linear dichroism of chlorophyll a and pheophytin a oriented in a liquid crystal1 has been reexamined. A combination of resolution enhancement of the spectra involving their Fourier transformation and manipulation in the Fourier domain, and deconvolution into Gaussian bands on the wavenumber scale has produced results conforming to previous conclusions that place the origin of the Q(X) transition in chlorophyll a some 800-900 cm-1 to the blue relative to the origin of the Q(Y) transition. In pheophytin a, however, the separation between the Q(X) and Q(Y) bands is much larger, about 3600 cm-1. The results also confirm previous reports of an angle near 70-degrees between the transition moment directions of the Q(Y) transitions and the molecular X-axis for both chlorophyll a and pheophytin a. The resolved vibronic bands in the case of the Q(Y) transition of chlorophyll a, at least, have their counterparts in both solution spectra and high-resolution low-temperature fluorescence excitation spectra.
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| 362. |
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| 363. |
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| 364. |
- Olesiak-Banska, J., et al.
(författare)
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Nonlinear absorption spectra of ethidium and ethidium homodimer
- 2012
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Ingår i: Chemical Physics. - : Elsevier BV. - 0301-0104. ; 404, s. 33-35
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Tidskriftsartikel (refereegranskat)abstract
- The Z-scan technique was used to determine the spectral dependence of the nonlinear absorption in well-known DNA intercalators: ethidium bromide and its homodimer. It is found that the compounds show essentially the same features of their nonlinear absorption spectra with the magnitudes of the relevant cross sections scaling with molecular weight of chromophore compound.
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| 365. |
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| 366. |
- Pall, Marita E., 1959, et al.
(författare)
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The transcription factor C/EBP-b and its role in ovarian function; evidence for direct involvement in the ovulatory process
- 1997
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Ingår i: The EMBO Journal. - : Wiley. - 0261-4189 .- 1460-2075. ; 16:17, s. 5273-5279
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Tidskriftsartikel (refereegranskat)abstract
- Gonadotropins are responsible for maturation of the ovarian follicle and the oocyte. Ovulation is the ultimate step in this process and involves disintegration of the follicular wall and subsequent release of an oocyte into the oviduct. These events are triggered by a surge of luteinizing hormone (LH), Genes expressed in the ovary, that respond to LH, are likely to be involved in the biochemical pathways that regulate ovulation, The transcription factor C/EBP-beta is induced promptly in the ovary, as a response to an ovulatory dose of gonadotropins. We used an ex vivo perfusion system to demonstrate that a specific reduction in ovarian C/EBP-beta expression inhibits ovulation, In such ovaries the oocytes appeared to be entrapped within the follicle. We have found a correlation between the expression level of the activating isoform of C/EBP-beta and the number of oocytes ovulated in response to gonadotropins, Since a reduction in C/EBP-beta expression does not affect the level of the ovulatory mediator prostaglandin endoperoxide synthase-2 (PGS-2), these findings support the view of C/EBP-beta as an important factor in the ovulatory process and highlight a C/EBP-beta-dependent and PGS-2-independent pathway that takes part in regulation of ovulation.
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| 367. |
- Papp, Dóra, et al.
(författare)
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Structural water stabilizes protein motifs in liquid protein phase: The folding mechanism of short β-sheets coupled to phase transition
- 2021
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 22:16
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Tidskriftsartikel (refereegranskat)abstract
- Macromolecular associates, such as membraneless organelles or lipid-protein assemblies, provide a hydrophobic environment, i.e., a liquid protein phase (LP), where folding preferences can be drastically altered. LP as well as the associated phase change from water (W) is an intriguing phenomenon related to numerous biological processes and also possesses potential in nanotechnological applications. However, the energetic effects of a hydrophobic yet water-containing environment on protein folding are poorly understood. Here, we focus on small β-sheets, the key motifs of proteins, undergoing structural changes in liquid–liquid phase separation (LLPS) and also model the mechanism of energy-coupled unfolding, e.g., in proteases, during W → LP transition. Due to the importance of the accurate description for hydrogen bonding patterns, the employed models were studied by using quantum mechanical calculations. The results demonstrate that unfolding is energetically less favored in LP by ~0.3–0.5 kcal·mol−1 per residue in which the difference further increased by the presence of explicit structural water molecules, where the folded state was preferred by ~1.2–2.3 kcal·mol−1 per residue relative to that in W. Energetics at the LP/W interfaces was also addressed by theoretical isodesmic reactions. While the models predict folded state preference in LP, the unfolding from LP to W renders the process highly favorable since the unfolded end state has >1 kcal·mol−1 per residue excess stabilization.
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| 368. |
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| 369. |
- Persson, Daniel, 1972, et al.
(författare)
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Penetratin-induced Aggregation and Subsequent Dissociation of Negatively Charged Phospholipid Vesicles
- 2001
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Ingår i: FEBS Letters. - 1873-3468 .- 0014-5793. ; 505:2, s. 307-312
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of the cellular delivery vector penetratin with a model system consisting of negatively charged phospholipid vesicles has been studied. Above a certain peptide to lipid molar ratio, the cationic oligopeptide induces vesicle aggregation. Interestingly, the aggregation is followed by spontaneous disaggregation, which may be related to membrane translocation of the peptide. Circular dichroism (CD) measurements indicate a conformational transition, from alpha -helix to antiparallel beta -pleated sheet, which is simultaneous with the aggregation process. The potential influence of spectroscopic artifacts on CD data due to the drastically increased turbidity during aggregation is discussed.
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| 370. |
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