Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Azides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,675 records · Page 93Linked to original sources
PubMedDate not supplied

Studies on the stability of rat testis membrane receptors for hLH, hCG and hFSH.

Receptor preparations from rat testes were stored at 4 C with various protease inhibitors and chemicals, at -20 C and -80 C, in freeze-dried form as well as at 4 C and 37 C after reconstitution in various media. Each preparation was tested for stability in terms of binding capacity of human luteinizing hormone (hLH), human chorionic gonadotropin (hCG) and human follicle-stimulating hormone (hFSH). The freeze-dried samples were stable for at least six months, although once reconstituted and stored at 4 C, they were less stable than fresh ones. Furthermore, Na azide and Na azide with diisopropylfluoro-phosphate (DIFP) prolonged the stability of the fresh samples. The samples stored at -20 C or -80 C were stable for at least 90 days and repeated freezing and thawing (15 times) did not change the binding capacity of either the hCG/hLH or hFSH receptors.

Animals↗
PubMed2003

A stone farm: development of a method for simultaneous production of multiple calcium oxalate stones in vitro.

We have previously shown how individual calcium oxalate stones of about 1 cm can be grown in vitro. While this proved a design concept, it was severely limited as an experimental tool because of the time required to undertake comparative studies. Here we describe a development of this system in which six parallel pairs of stone generators are supplied with feed solutions generating a medium that is supersaturated with calcium oxalate. Twelve stones were grown simultaneously in aseptically prepared artificial urine over a period of 32 days from 100 mg to about 250 mg. Flow rates, pH and [Ca(2+)] were stable and reproducible over the course of the experiment. Sodium azide (0.02%) was included in the growth medium of six stones and caused a modest decrease in growth rate from 5.5 to 3.4 mg/day. The experimental design is such that this was readily detectable both visually and statistically ( p<0.001). This multiple stone growing system ("a stone farm") shows improved consistency and illustrates the statistical power of the technique. Azide has only a minor effect on the growth kinetics and can be used as an antibacterial agent in studies involving urinary macromolecules. The technique is suitable for practical and meaningful investigation of calcium oxalate stone formation in vitro.

Calcium Oxalate↗
PubMed2003

Isolation and characterization of bacteria capable of degrading phenol and reducing nitrate under low-oxygen conditions.

Nitrate-reducing bacteria capable of degrading phenol were isolated from natural and contaminated environments under low-oxygen conditions with nitrate-containing media, using phenol as a sole carbon and energy source. A total of 27 bacteria able to degrade phenol and reduce nitrate under low-oxygen conditions were isolated from all of the inoculum samples, regardless of previous phenol contamination. For all of these bacteria, oxygen was an essential requirement for phenol degradation. Nitrate reduction by 19 of the strains was insensitive to 10 mM sodium azide, and these strains were placed into the alpha- and beta-subclasses of Proteobacteria and two were Gram-positive bacteria. To date, the order of Rhizobiales has hardly been reported to have an ability to degrade aromatic compounds. Interestingly, our study showed that all isolates that were placed into the alpha-subclass of Proteobacteria are in the order of Rhizobiales. Furthermore, the genus Agrobacterium was isolated from most inoculum samples and one genus of Gram-positive bacteria, Staphylococcus, was also isolated. In the case of the remaining eight strains, nitrate reduction was inhibited by 10 mM sodium azide. Of these strains, seven were placed into the gamma-subclass of Proteobacteria.

Alphaproteobacteria↗
PubMed2000

ATP-sensitive potassium channels in freshly dissociated adult rat striatal neurons: activation by metabolic inhibitors and the dopaminergic receptor agonist quinpirole.

The characteristics of adenosine 5'-triphosphate (ATP)-sensitive K+ channels in acutely isolated striatal neurons from adult rats were examined. Neurons had a resting membrane potential of -53.9+/-1.2 mV (n=66), with evoked or spontaneous action potentials firing at 10+/-0.7 Hz, and large inwards and outwards whole-cell currents. In cell-attached patches with a high [K+] in the pipette, a voltage-independent, ATP-insensitive 16.5+/-1.5 pS channel was observed in 375 out of 452 cells. Bath application of Na+-azide (0.5-2 mM) to 108 neurons revealed another 145.7+/-3.5 pS (LKATP) channel in 65 neurons; this channel was blocked by tolbutamide. The LKATP channel exhibited a high open probability (Po, 0.8+/-0.05) at 0 mV pipette potential. Varying the pipette [K+] shifted the reversal potential of LKATP, showing the channel's K+ selectivity. Cytoplasmic ATP (ATPi) reversibly inhibited LKATP, with an inhibitory constant (Ki) of 0.12 mM. LKATP was sensitive to intracellular Ca2+ but insensitive to iberiotoxin. In 25% of cell-attached patches, the presence of quinpirole in the pipette opened a third type of channel (90.6+/-1.7 pS, termed D2KATP). Sulpiride, a dopamine D2-receptor antagonist, inhibited D2KATP. ATPi reversibly inhibited D2KATP, with a Ki of 0.212 mM. The Na+-azide- or quinpirole-induced current caused a tolbutamide-sensitive membrane hyperpolarization and a marked reduction in action potential frequency. We propose that ATP-sensitive K+ channels play a metabolism-dependent role in striatal neurons.

Action Potentials↗
PubMed2003

Inhibition of energy metabolism down-regulates the Alzheimer related presenilin 2 gene.

Defects in energy metabolism and oxidative stress play an important role in the pathogenesis of Alzheimer's Disease (AD). In sporadic AD cases, presenilin 2 (PS2) mRNA levels are decreased in brain areas affected by the disease. The aim of the present study was to investigate whether mitochondrial dysfunction might influence PS2 gene expression. We demonstrated that the inhibition of energy metabolism by sodium azide down-regulates PS2 gene expression through modification of promoter activity. No one of the analyzed transcription factors, sensitive to redox status of the cell, could explain this effect. Azide effect on PS2 expression was completely inhibited by the addition of an antioxidant suggesting that the imbalance of the cellular redox homeostasis modulates the expression of this gene.

Alzheimer Disease↗
PubMed2003

Rat models of dementia based on reductions in regional glucose metabolism, cerebral blood flow and cytochrome oxidase activity.

Three models are described in rats which attempt to mimic morphological and behavioural pathology of Alzheimer's dementia; intracerebroventricular injection of streptozotocin (STZ), permanent bilateral carotid artery occlusion (2VO) and brain mitochondrial cytochrome oxidase inhibition by sodium azide. Learning and memory are impaired within 4 weeks in all models. This probably involves a reduction in cortical and/or hippocampal cholinergic neurotransmission. STZ causes microglial activation and specific damage to myelinated tracts in the fornix through generation of oxidative stress, thereby disrupting connections between the septum and hippocampus. 2VO results in damage to myelin and CA1 cells in hippocampus and in abnormal processing of APP to beta-amyloid. It is not known if microglial activation and neuronal damage occur after sodium azide administration. Memory and learning can be improved in the STZ and 2VO models by estradiol, melatonin and cholinesterase inhibitors. Antioxidants and neuroprotective agents may also decrease memory deficits by preventing inflammation and neurodegeneration.

Animals↗
PubMed2000

Binding of nitrite and its reductive activation to nitric oxide at biomimetic copper centers.

The reactivity of nitrite towards the copper(II) and copper(I) centers of a series of complexes with tridentate nitrogen donor ligands has been investigated. The ligands are bis[(1-methylbenzimidazol-2-yl)methyl]amine (1-bb), bis[2-(1-methylbenzimidazol-2-yl)ethyl]amine (2-bb), and bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine (ddah) and carry two terminal benzimidazole (1-bb, 2-bb) or pyrazole (ddah) rings and a central amine donor residue. While 2-bb and ddah form two adjacent six-membered chelate rings on metal coordination, 1-bb forms two smaller rings of five members. The binding affinity of nitrite and azide to the Cu(II) complexes (ClO4- as counterion) has been determined in solution. The association constants for the two ligands are similar, but nitrite is a slightly stronger ligand than azide when it binds as a bidentate donor. The X-ray crystal structure of the nitrite complex [Cu(ddah)(NO2)]ClO4 (final R=0.056) has been determined: triclinic P1space group, a=8.200(2) A, b=9.582(3) A, c=15.541(4) A. It may be described as a perchlorate salt of a "supramolecular" species resulting from the assembly of two complex cations and one sodium perchlorate unit. The copper stereochemistry in the complex is intermediate between SPY and TBP, and nitrite binds to Cu(II) asymmetrically, with Cu-O distances of 2.037(2) and 2.390(3) A and a nearly planar CuO2N cycle. On standing, solutions of [Cu(ddah)(NO2)]ClO4 in methanol produce the dinuclear complex [Cu(ddah)(OMe)]2(ClO4)2, containing dibridging methoxy groups. In fact the crystal structure analysis (final R=0.083) showed that the crystals are built up by dinuclear cations, arranged on a crystallographic symmetry center, and perchlorate anions. Electrochemical analysis shows that binding of nitrite to the Cu(II) complexes of 2-bb and ddah shifts the reduction potential of the Cu(II)/Cu(I) couple towards negative values by about 0.3 V. The thermodynamic parameters of the Cu(II)/Cu(I) electron transfer have also been analyzed. The mechanism of reductive activation of nitrite to nitric oxide by the Cu(I) complexes of 1-bb, 2-bb, and ddah has been studied. The reaction requires two protons per molecule of nitrite and Cu(I). Kinetic experiments show that the reaction is first order in [Cu(I)] and [H+] and exhibits saturation behavior with respect to nitrite concentration. The kinetic data show that [Cu(2-bb)]+ is more efficient than [Cu(1-bb)]+ and [Cu(ddah)]+ in reducing nitrite.

Anaerobiosis↗
PubMed1984

New fluorogenic, photoactivable, heterobifunctional crosslinking thiol reagents.

Properties of newly synthesized crosslinking reagents (ACM) and their applications to proteins are studied (ACM is the abbreviation for a series of photoactivable and heterobifunctional crosslinking thiol reagents, each of which has two reactive groups, maleimide and azide). These reagents bind specifically to the sulfhydryl residues of proteins in the first reaction step. Upon photoactivation, the azide group of the coumarin ring reacts with side or main chains of the proteins, and thus intra- or intermolecular crosslinking can be elicited. In addition, the coumarin moiety of the reagents becomes highly fluorescent after photolysis. Therefore, the crosslinking products can be detected by fluorometry with high sensitivity in the pattern of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Reaction of ACM with rabbit muscle aldolase led to extensive crosslinking between subunits of the enzyme and maximally 25% of the total subunits were found to be crosslinked to the dimer.

Acetylcysteine↗
PubMed1985

1H NMR spectroscopy of cytochrome cd1 derivatives.

Proton nuclear magnetic resonance spectra are reported for cytochrome cd1 from Pseudomonas aeruginosa (ATCC 19429) in several forms including complexes of the ferricytochrome with cyanide, azide, and fluoride, a quasi-apo form in which the noncovalently associated heme d1 has been removed but the covalently bound heme c is retained, and the reduced state of both native and the quasi-apo forms. Comparisons are made to the previously reported spectrum of ferricytochrome cd1. The following points are made. The spectra of the azide and fluoride complexes and the ferric quasi-apo form show perturbation of resonances assignable to the site of heme d1, and leave relatively unperturbed resonances assignable to the site of heme c. The heme d1 associated resonances are at 46.0, 35.4, 23.3, 17.5, -2.9, and 16 ppm, and the heme c associated resonances are at 42.0, 33.7, 15.0, 13.9, -7.5, -14, and -33 ppm in native ferricytochrome cd1. The similarity of the hyperfine resonances of the ferric quasi-apo from to the heme c resonances of intact ferricytochrome cd1 is evidence that removal of heme d1 leaves the heme c binding site relatively unaltered. Linewidths and relaxation times suggest that the relaxation times of the unpaired electron spins of the ferric hemes c and d1 are on the same order of magnitude. Although it is paramagnetic, ferrocytochrome cd1 does not demonstrate an experimentally detectable hyperfine shifted spectrum under present conditions. Possible reasons for this are discussed. The presence of a narrow resonance at -2.8 ppm in both ferrocytochrome cd1 and the reduced state of the quasi-apo form suggests that methionine may be a ligand to heme c.

Azides↗
PubMed1992

Adenine nucleotide-binding sites on mitochondrial F1-ATPase: studies of the inactive complex formed upon binding ADP at a catalytic site.

ADP-induced inhibition of mitochondrial F1-ATPase has been studied. It is shown that in the presence of magnesium and the absence of light, the photoaffinity ADP analog, 2-azido-ADP, induces a reversible inhibition of native F1 that is indistinguishable from that obtained with ADP. Photolysis of the inactive complex results in the predominant labeling of a catalytic-site peptide identified previously (Cross et al., 1987, Proc. Natl. Acad. Sci. USA 84, 5715-5719). Dissociation of the inactive complex formed between F1 and ADP is biphasic with a rapid azide-insensitive phase followed by a slow azide-sensitive phase (k approximately 3 x 10(-3) s-1). It is also shown that incubation of the ADP-inhibited enzyme with EDTA or phosphate does not result in release or migration of ADP from the catalytic site. However, it does convert the complex to a form that reactivates in the presence of 100 microM ATP at a rate too rapid to observe using manual mixing.

Adenosine Diphosphate↗
PubMed1975

The effect of sulphide on cytochrome aa3. Isosteric and allosteric shifts of the reduced alpha-peak.

1. Sulphide, like cyanide, is a slow-binding inhibitor of cytochrome aa3 with a high affinity (KD smaller than 0.1 MUM). 2. Unlike cyanide binding, the binding of sulphide is apparently independent of the redox state of components of the oxidase other than cytochrome a3 and shows no anomalous kinetics during complex formation. 3. Sulphide binding to cytochrome a3-3+ is accompanied by a blue-shift in the alpha-peak of the reduced enzyme (a-2+ a3-3+ H2S), similar to but smaller than that induced by azide. 4. The reduced sulphide-inhibited system shows a much higher Soret peak at 445 nm than the corresponding cyanide and azide complexes, suggesting that partial electron transfer from sulphide to haem may occur in the complex. No evidence was obtained for the formation of any sulfhaem derivatives of cytochrome a3. 5. The influence of energization on the spectrum of mitochondrial cytochrome oxidase, and the effects of calcium on the alpha-peak of isolated cytochrome aa3 (Wikström, M.K.F. (1974) Ann. N.Y. Acad. Sci. 227, 146-158) are distinct from the action of the cytochrome a3 ligands. 6. A classification of peak shifts in the alpha-region in terms of isosteric and allosteric ligands is proposed.

Animals↗
PubMed1977

The effect of inhibitors on the oxygen kinetics of cytochrome c oxidase.

1. The oxygen kinetics of purified beef heart cytochrome c oxidase were investigated. 2. The effect of addition of various fixed concentrations of the inhibitors CO, HN3, HCOOH, HCN and H2S on the double reciprocal plot of respiration rate against oxygen concentration was studied. 3. CO is strictly competitive, azide and formate are uncompetitive, and cyanide and sulfide are non-competitive inhibitors towards oxygen. 4. Binding constants for the various inhibitors from secondary plots of the oxygen kinetics at pH 7.4 are: CO: Ki = 0.32 micronM, azide: Ki = 33 micronM; formate: Ki = 15 mM; cyanide: Ki = 0.2 micronM and sulfide: Ki = 0.2 micronM. 5. The possible significance of these results in the elucidation of the reaction mechanism is discussed.

Animals↗
PubMed1978

Responses of the a3 component of cytochrome c oxidase to substrate and ligand addition.

We have previously described a transient high spin ferric heme species in cytochrome c oxidase (EC 1.9.3.1) which represent a3+(3) (Beinert, H. and Shaw, R.W.(1977) Biochim. Biophys. Acta 462, 12u--130), and can be detected and quantitatively determined by EPR. We have now used out ability to generate this species to study reactions of a3+(3) with substrates and ligands and also responses to pH changes. This was accomplished by multiple rapid mixing and freezing techniques in conjunction with low temperature EPR and optical reflectance spectroscopies. The substrates used were O2 and ferrocytochrome c and the ligands cyanide, sulfide, azide and carbon monoxide. Contrary to the oxidized, resting form of the enzyme, the transient high spin species of a3+(3) reacts within less than 10 ms stoichiometrically with cyanide and sulfide and at a slower rate with azide. The transient a3+(3) species responds to O2 and CO by changes in signal size or shape, although no oxidoreduction is involved, indicating that a3+(3) registers the presence of these gases. The high spin signal of the transient species is readily abolished by ferrocytochrome c or on raising the pH. Decreasing the pH induces a shift from the rhombic towards the axial component of the signal. Since the responses to CO and pH are analogous for the rhombic transient species to those observed with the rhombic high spin ferric heme species produced on partial reduction, it is suggested that the rhombic signals represent a3+(3) in either case. In all these experiments, in which EPR detectable a3+(3) was observed in large yield, no extra signals for copper or correspondingly increased intensity in the copper signal at g = 2 were seen. The relationship is discussed of the obviously reactive transient species of a3+(3) to other 'activated' species that have been reported and to the oxidized resting form of the enzyme, which is known to react only slowly with ligands and to respond sluggishly to substrate.

Azides↗
PubMed1979

Sugar transport in Coprinus cinereus.

Two transport systems for glucose were detected: a high affinity system with a Km of 27 muM, and a low affinity system with a Km of 3.3 mM. The high affinity system transported glucose, 2-deoxy-D-glucose (Km = 26 muM), 3-O-methylglucose (Km = 19 muM), D-glucosamine (Km = 652 muM), D-fructose (Km = 2.3 mM) and L-sorbose (Km = 2.2 mM). All sugars were accumulated against concentration gradients. The high affinity system was strongly or completely inhibited by N-ethylmaleimide, quercetin, 2,4-dinitrophenol and sodium azide. The system had a distinct pH optimum (7.4) and optimum temperature (45 degrees C). The low affinity system transported glucose, 2-deoxy-D-glucose (Km = 7.5 mM), and 3-O-methylglucose (Km = 1.5 mM). Accumulation again occurred against a concentration gradient. The low affinity system was inhibited by N-ethylmaleimide, quercetin and 2,4-dinitrophenol, but not by sodium azide. The rate of uptake by the low affinity system was constant over a wide temperature range (30--50 degrees C) and was not much affected by pH; but as the pH of the medium was altered from 4.5 to 8.9 a co-ordinated increase in affinity for 2-deoxy-D-glucose (from 52.1 mM to 0.3 mM) and decrease in maximum velocity (by a factor of five) occurred. Both uptake systems were present insporelings germinated in media containing sodium acetate as sole carbon source. Only the low affinity system could initially be demonstrated in glucose-grown tissue, although the high affinity system was restored by starvation inglucose-free medium. The half-ti me for restoration of high affinity activity was 3.5 min and the process was unaffected by cycloheximide. Addition of glucose to an acetate-grown culture inactivated the high affinity system with a half-life of 5--7.5 s. Addition of cycloheximide to an acetate-grown culture caused decay of the high affinity system with a half-life of 80 min. Regulation is thus thought to depend on modulation of protein activity rather than synthesis, and the kinetics of glucose, 2-deoxy-D-glucose and 3-O-methylglucose uptake would be consistent with there being a single carrier showing negative co-operativity. Analysis of transport defective mutants revealed defects in both transport systems although the mutants used were alleles of a single gene. It is concluded that this gene (the ftr cistron) is the structural gene for an allosteric molecule which serves both transport systems.

Agaricales↗
PubMed1980

The interaction of myeloperoxidase with ligands as studied by EPR.

1. The reaction of myeloperoxidase with fluoride, chloride and azide has been studied by EPR. 2. Fluoride decreases the rhombicity of the high-spin heme signal of myeloperoxidase and the nuclear spin of the fluoride atom induces a splitting in g parallel of 35 G. This observation demonstrates that fluoride binds as an axial ligand to the heme iron of the enzyme. 3. Addition of chloride to the fluoride-treated enzyme increases the rhombicity of the high-spin heme signal and brings about a disappearance of the splitting at g parallel. The addition of azide to the fluoride-treated enzyme changes the spin state of the heme iron from a high-to a low-spin state (gx = 2.68, gy = 2.22 and gz = 1.80). 4. Upon addition of chloride or fluoride to low-spin azido-myeloperoxidase this compound is converted into the high-spin chlorido- or fluorido-myeloperoxidase. These observations demonstrate that these ligands compete for a binding site at or close to the heme iron of myeloperoxidase.

Azides↗
PubMed1980

EPR spectroscopy of semi-methemerythrin.

EPR spectra of semi-met forms of octameric hemerythrin from Themiste zostericola, prepared by one electron reduction of methemerythrin or by one electron oxidation of deoxyhemerythrin, have been visualized at liquid helium temperatures. The spectrum of that prepared by one electron reduction has principal g-values of 1.96 +/- 0.01, 1.88 +/- 0.01, and 1.67 +/- 0.02 while that obtained by one electron oxidation has g = 1.95 +/- 0.01, 1.72 +/- 0.01, and 1.68 +/- 0.02. The amplitude of either spectrum decreases with time on incubation at room temperature according to a first order rate with t 1/2 = 5-8 min, apparently because of an intramolecular disproportionation. Similar EPR spectra have been obtained with semi-metmyohemerythrin of T. zostericola and with the octameric semi-met form of Phascolopsis gouldii. However, these forms disproportionate to a much lesser degree. The azide adduct of the octameric semi-met form of T. zostericola has g-values of 1.94 +/- 0.01, 1.85 +/- 0.01, and 1.57 +/- 0.02. Its EPR spectrum differs somewhat from those of the azide adducts of the octamer of P. gouldii and the monomer of T. zostericola although all are resistant to disproportionation. Methemerythrin and deoxyhemerythrin have no EPR spectra even at liquid helium temperature.

Animals↗
PubMed1995

Iron-stimulated ring-opening of benzene in a mouse liver microsomal system. Mechanistic studies and formation of a new metabolite.

In the present study, we investigated the mechanism(s) of ring-opening of benzene in a mouse liver microsomal system in the presence of Fe2+.HPLC analysis based on coelution with authentic standards and on-line UV spectra obtained using a diode array detector indicated that benzene is metabolized to phenol, hydroquinone (HQ), trans,trans-muconaldehyde (muconaldehyde, MUC), 6-oxo-trans,trans-2,4-hexadienoic (COOH-M-CHO), 6-hydroxy-trans,trans-2,4-hexadienal (CHO-M-OH), and 6-hydroxy-trans,trans-2,4-hexadienoic acid (COOH-M-OH). CHO-M-OH was confirmed by mass spectrometry. Muconaldehyde was also metabolized to CHO-M-OH, COOH-M-CHO and COOH-M-OH, in the same microsomal system. The inhibition of muconaldehyde metabolism by microsomes in the presence of pyrazole indicates that there is cytosolic alcohol dehydrogenase (ADH) activity in the microsomes. Metabolism by contaminating ADH of muconaldehyde formed during microsomal incubation of benzene could be involved in the formation of CHO-M-OH and COOH-M-OH. The ring-opening of benzene was stimulated by added Fe2+. Hydrogen peroxide was produced in the microsomal system and consumed in the presence of added Fe2+. Addition of catalase inhibited the formation of ring-opened products, while superoxide dismutase increased their formation in the presence of azide. Singlet oxygen scavengers, i.e. histidine, deoxyguanosine, Tris and azide (at concentrations above 1.0 mM), dramatically decreased the ring-opening of benzene. Hydroxyl radical scavengers, DMSO, mannitol and formate, but not ethanol, also decreased the ring-opening of benzene. The data indicate that Fenton chemistry plays an important role in benzene ring-opening by microsomes. An unknown peak with UV absorption maxima at 275 and 345 nm was also detected. Based on pH sensitivity of the UV spectrum, the reactivity with thiobarbituric acid (giving a chromogen with absorption maximum at 532 nm) and the molecular weight (126), this compound was identified tentatively as alpha- or beta-hydroxymuconaldehyde.

Aldehydes↗
PubMed1990

Biologically active aromatic retinoids bearing azido photoaffinity-labeling groups and their binding to cellular retinoic acid-binding protein.

Retinoids bearing azido photoaffinity-labeling groups (azidoretinoids) have potential as probes for investigating the molecular mechanisms of action of all-trans-retinoic acid (RA) as mediated by its cellular retinoic acid-binding protein (CRABP) and nuclear receptor proteins. Two new azidoretinoids, 3-azido-4-[2-(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)-1E- propen-1-yl]-benzonic acid and 4-(4-azido-5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-anthracenyl)be nzoic acid were synthesized, and evaluated for their in vitro biological potency, and binding affinity for CRABP. Like RA, these aromatic azides had significant activity in modulating cell differentiation in retinoid-deficient hamster tracheal organ culture (ED500.02 nM and 0.03 nM, respectively) and in the inhibition of the induction of ornithine decarboxylase in mouse epidermis (ED50 7.0 nmol and 0.5 nmol, respectively). They also possessed high binding affinity for CRABP (ID50 0.9 microM and 0.85 microM, respectively). The tritiated aromatic azides were further evaluated for their ability to bind covalently to CRABP after photolysis. On photolysis at -78 degrees C, the two radiolabeled azidoretinoids formed stable adducts with CRABP. Treatment of the adducts with either RA or p-chloromercuriphenylsulfonic acid (CMPS) and subsequent dialysis did not cause any dissociation, indicating the formation of a covalent bond. In contrast, treatment of the unirradiated complexes with RA or CMPS led to dissociation of the complex. Synthesis of affinity labels and characterization of CRABP-retinoid complexes should provide useful information on the ligand-binding regions and insights into the mechanism of action of RA.

Affinity Labels↗