Soret maximum

The alteration of hemoprotein(s) P-450 subpopulations in the rat may be observed spectrally, because after treatment of rats with polycyclic aromatic hydrocarbons, the Soret maximum of the carbonmonoxyferrocytochrome complex undergoes a hypsochromic shift from 450 to 448nm (50). This blue shift was not seen with rainbow trout hepatic microsomes (29,30). However, this does not preclude the induction of novel hemoproteins P-450 since (a) the induced hemoprotein(s) maty not differ spectrally from the constitutive enzymes and (b) the induced-hemoprotein may account for only a small proportion of total hemoprotein P-450, and hence its contribution to the position of the Soret maximum of carbon monoxide-treated reduced microsomes may be negligible. The latter suggestion is supported by the work of Bend et al. with the little skate. These workers have shown that hepatic microsomes from 1, 2,3,4-dibenzanthracene treated skates did not exhibit a hypsochromic shift when compared to control microsomes, however, partially purified hemoprotein exhibited an absorbance maxima at 448 nm (51). 

Although the heme-binding N-terminal half of NOS bears no sequence similarity to P450s, the spectral properties of the Fe +-CO complex with the characteristic 450 nm Soret maximum (72-74) clearly places NOS in the category of P450-like thiolate enzymes. The architecture of NOS also is strikingly similar to cytochrome P450BM-3 (75)... 

Hm = histamine), which results in a shift in the Soret maximum from near 420 nm to near 413 nm. In conditions of large histamine excess, histamine binds rapidly relative to NO and with high affinity (50). The first-order rate constant for NO release was estimated in a displacement reaction using... 

The experiments on CO forms of the synthetic compounds were done with sample concentrations adjusted to 50 pM to give an absorbance of 1 over a 1 mm optical path at the Soret maximum. For the oxygen experiments, the samples were prepared as the CO complexes and covered with a balloon containing 3 1 mixture of CO to O. An additional photographic strobe lamp having a flash duration... 

Clezy and Morrell (61) discuss the appearance of different absorption spectra for a given porphyrin in different solvents and the effect of changing the substituents at the porphyrin perifery. In acetic acid there was only a single Soret maximum at 410—425 nm while in acetone, chloroform, ether and benzene a double Soret band was seen in the region 350—390 nm. It is probable that only one of these bands is really a Soret band and that the higher energy band is probably a forbidden transition. In a similar study, Whitten, Baker, and Corwin (62) examined the... 

Optical absorption spectra of the hydroperoxo-ferric intermediate in HO64 show Soret maximum at 421 nm (5 nm red shifted as compared with 416 nm band for oxy-ferrous HO) and Q-bands at 530 and 557 nm. After annealing at 212-215 K, a new species is formed with Soret band at 406 nm characteristic for the o-meso-hydroxyheme. 

Most Phase I oxidations are performed by cytochrome P-450. "Cytochrome," derived from Greek, literally means "colored substance in the cell." The color is derived from the properties of the outer electrons of the transition element iron. "P-450" denotes a reddish pigment with the unusual property of having its major optical absorption peak (Soret maximum) at about 450 nm, when it has been reduced and combined with carbon monoxide.330 Although the name "P-450" was intended to be temporary (until more was known about the substance), the terminology has persisted for 18 yr because of the increasing complexity of this enzyme system and because of the lack of agreement on new nomenclature. 

The apparent discrepancy between the RFQ and stopped-flow experiments was recently ascribed to differences in pH between the two studies. The pH influences the pre-equilibrium concentrations between Cpd I (Soret maximum at 367 nm) and the Y 96 radical intermediate (Soret maximum at 406 nm) ... 

Dyads (1 - 4) were synthesized by the method described previously. Fluorescence spectra were measured in degassed acetonitrile solutions at 2S °C with a Hitachi 8S0 spectrofluorometer. The excitation wavelength was the Soret maximum. Fluorescence lifetimes were measured at 25 °C using a Horiba NAES-500 ns-fluorometer interfaced to an NEC PC-9801 RX personal computer. The excitation light below 420 nm was cut off with a glass filter. The fluorescence was detected by a single-photon counting system and analyzed as the sum of two exponential components after deconvolution of the instrument response function. NMR spectra were recorded on a JEOL JNM GX-270 NMR spectrometer. 

TRZ that exhibit a Soret maximum at 424 or 422 nm, respectively, and thus are red shifted from the absolute CYP3A4 spectrum (416 nm Soret maximum) by 6 and 8 nm, respectively [128], The Soret red shift of the CYP3A4-1,2,3-TRZ-EE complex on the other hand was of the... 

Figure 1. Electron transport chains of the endoplasmic reticulum. (A) Microsomal acyl-Co A desaturation system composed of NADH-cytochrome reductase, cytochrome fos (a flavoprotein), and fatty acyl-CoA desaturase. (B) Microsomal hydroxylase system depicting participation of the NADPH-cytochrome P-450 reductase (a flavoprotein), cytochrome P-450, and phosphatidylcholine. The role of the phospholipid appears to be in enhancing interaction of the proteins. The reduced form of the hemoprotein cytochrome P-450, on addition of carbon monoxide, envinces a Soret maximum at 450 nm, accounting for its designation. There is evidence that these two systems (A and B) interact in the membrane.

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