SEARCH · PubMed Health

Results for “D4H”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

6 recordsLinked to original sources

PubMed2025

Use of the D4H Probe to Track Sterols in Yeast.

Cholesterol is a fundamental component of cellular membranes, and its organization, distribution, and recycling are tightly regulated. Cholesterol can form, together with other lipids and proteins, membrane nanodomains, which play important roles in membrane trafficking, the spatiotemporal organization of signal transduction, or the modulation of plasma membrane transporters, among others. Not surprisingly then, the misregulation of cholesterol biosynthetic and transport pathways has been related to numerous diseases, including neurodegenerative and metabolic disorders. Here, we focus on the cholesterol-binding domain 4 (D4) of perfringolysin O (PFO, theta toxin) and its use as a probe to define the dynamics and subcellular localization of yeast sterols using time-lapse live-cell fluorescence microscopy. In combination with drugs that acutely interfere with sterol synthesis, such as terbinafine, the probe can also be used to monitor in real-time the extraction of sterols from specialized endoplasmic reticulum subdomains named ERSES (endoplasmic reticulum sterol exit sites) by the OSBP-related protein Osh2.

Saccharomyces cerevisiae↗

PubMedDate not supplied

[Effect of further complexing on the spectral-luminescent properties of Mg-porphyrins].

It has been shown by investigations of polarization spectra and the dependence of the degree of fluorescence and phosphorescence polarization on emission wavelength that in non-polar solvents at 77 degrees K the molecules of Mg porphin and Mg tetraphenylporphin possess true symmetry D4h. When polar molecules (water, alcohols, pyridine) are present in the solution further complexing of the magnesium complexes with extra-ligands takes place and the polarization data indicate that D4h symmetry is absent which leads to splitting of the doubly degenerate states by 100-150 cm-1. It has been established that on further complexing the S1 and T1 levels are lowered by approximately 500 and 700 cm-1, respectively, the probability of intercombinational degradation T1 leads to S0 increases in this case. It follows from the data obtained that the extra-ligands do not essentially influence spin-orbit interaction.

Alkanes↗

PubMed1976

Infrared magnetic circular dichroism of myoglobin derivatives.

By use of a newly constructed CD instrument, infrared magnetic circular dichroism (MCD) spectra were observed for various myoglobin derivatives. The ferric high spin myoglobin derivatives such as fluoride, water and hydroxide complexes, commonly exhibited the MCD spectra consisting of positive A terms. Therefore, the results reinforced the assignment that the infrared band is the charge transfer transition to the degenerate excited state (eg (dpi)). Since the fraction of A term estimated was approximately 80% for myoglobin fluoride and approximately 35% for myoglobin water, the effective symmetry for myoglobin fluoride is determined to be as close as D4h, while that for myoglobin water seems to have lower symmetry components. The ferric low spin derivatives such as myoglobin cyanide, myoglobin imidazole and myoglobin azide showed positive MCD spectra which are very similar to the electronic absorption spectra. These MCD spectra were assigned to the charge transfer transitions from porphyrin pi to iron d orbitals on the ground that they were observed only for the ferric low spin groups and insensitive to the axial ligands. The lack of temperature dependence in the MCD magnitude indicated that the MCD spectra are attributable to the Faraday B terms. Deoxymyoglobin, the ferrous high spin derivative, had fairly strong positive MCD around 760 nm with an anisotropy factor (delta epsilon/epsilon) of 1.4-10(-4). It shows some small MCD bands from 800 to 1800 nm. Among the ferrous low spin derivatives, carbonmonoxymyoglobin did not give any observable MCD in the infrared region while oxymyoglobin seemed to have significant MCD in the range from 700 to 1000 nm.

Animals↗

PubMed1977

CNDO molecular orbital calculations on porphyrins--II. Ground states of dilithium and disodium porphyrin.

CNDO/2 calculations are reported for dilithium and disodium porphyrin. The total energy is calculated as a function of the metal-ring distance for symmetrical (D4h) structures. For dilithium porphyrin, the equilibrium metal-ring distance is 0.87 A and the metal-metal vibrational frequency is 123 cm-1. For disodium porphyrin, the distance is 1.64 A and the frequency is 77 cm -1. Little mixing of metal and porphyrin orbitals takes place; the two lowest unoccupied and the two highest occupied MOs hardly differ from those in porphyrin, but lower MOs are considerably rearranged.

Lithium↗

PubMed1976

Magnetic circular dichroism on the reversible oxygenation of dimethylmesoporphyrin-IX-atopyridinecobalt (II).

The magnetic circular dichroism spectra were measured for the dimethylmesoporphyrin-IX-atocobalt complexes. As expected dimethylmesoporphyrin-IX-atocobalt (III) and its pyridine complex exhibited the MCD for a typical D4h metalloporphyrins. Dimethylmesoporphyrin-IX-atocobalt (II) and its pyridine complex showed a paramagnetic effect on the MCD especially in the Soret region. A very atypical Soret MCD for the oxygenated dimethylmesoporphyrin-IX-atopyridinecobalt (II) was attributed to the existence of a CT band associated with oxygen from the similarity to the MCD for oxymyoglobin. Temperature-dependent MCD change for the cobalt (II) oxygen complex revealed the reversible oxygen binding to dimethylmesoporphyrin-IX-atopyridinecobalt (II) with KO2 of 3.2 X 10(-3) in (mmHg)-1 at 228 degrees K.

Binding Sites↗

PubMed1975

[Studies on the magneto-optical rotation of porphyrins, hemins and methemoglobin compounds].

Using the method of magneto-optical rotation (MOR) various porphyrin derivatives, hemin and heme compounds, and a number of methemoglobin complexes were investigated. The spectra were recorded from 450-600 nm; with methemoglobin also in the Soret region. 1. The metalfree porphyrin derivatives (deutero-, meso-, hemato- and protoporphyrins) were measured in strongly acidic aqueous solution. The derivatives thus present as di-cations yield highly resolved MORspectra, where the Q-bands (Oo leads to; Oo leads to 1) originated from the pi-pi transitions of the porphyrin display the curve shape characteristic of an A-term, this proving the presence of the D4h symmetry. An exception is the protoporphyrin, in which the pi-electron system of the porphyrin is perturbed by the influence of pi-electrons of the vinyl group, causing poor resolution, line broadening, and shift of the Q-bands into the lower-energy spectral region. 2. With iron porphyrins (hemin, heme and their complexes) the charge of the iron and the nature of axial ligands determine the position and intensity of the O-bands in the MOR spectrum. Low-spin complexes have a higher symmetry than the high-spin complexes. Whereas with hemin (S = 5/2), the iron located outside the heme plane strongly disturbs the porphyrin pi-system, the high symmetry of porphyrin is greatly retained in the case of heme. This can be explained by the enhanced binding distance between the bivalent iron and the porphyrin to great for a strong coupling between the microsymmetry of the iron and the macrosymmetry of the porphyrin pi-system.

Heme↗