A study of the interaction between D-amino acid oxidase and quasi-substrates.

To study the interaction between D-amino acid oxidase [EC 1.4.3.3] and quasi-substrates such as benzoate and o-, m-, and p-aminobenzoate, visible circular dichroism spectra (CD spectra) were measured and the binding rate and affinity of o-aminobenzoate to the enzyme were observed by following the absorption changes at various wavelengths. We found a new CD band around 560 nm, corresponding to the charge-transfer complexes which result from the formation of aminobenzoate complexes with the enzyme. The ellipticity of this band was positive for the p-aminobenzoate complex, but negative for the o- and m-aminobenzoate complexes. Crossover points in CD spectra were observed at 470 nm for the m-aminobenzoate complex and at 475 nm for the o-aminobenzoate complex. They probably resulted from overlapping of the positive CD band of FAD bound with the enzyme and the negative CD band of the charge-transfer complex. We propose that the amino group in aminobenzoate, not the pi-electrons of the benzene ring, is the electron donor in the charge-transfer complex and that the position of the amino group is very important for the charge-transfer interaction. The binding rate and affinity of o-aminobenzoate to the enzyme were determined using the absorption changes at 370 nm (380 nm), caused by the modification of electronic states of FAD bound with the enzyme, and at 550 nm (565 nm), caused by the formation of the charge-transfer complex of o-aminobenzoate with the enzyme. No differences between these parameters with wavelength were observed. This independence of wavelength simplifies discussion of the experimental data obtained from absorption changes.     

Bioinorganic study on [Fe(promethazine)2H2O Cl]2+ complex

The coordination chemistry of iron (III) is the environment of an antihistaminic drug, promethazine has been explained to include a low spin, six-coordinate complex [Fe(Prometha)2(H2O) Cl] Cl2. Metaldrug interaction in vitro in aqueous KCl phase was studied polarographically at physiological pH and temperature. On the basis of elemental, magnetic, conductometric, IR, UV-visible, NMR spectroscopic analysis it is concluded that in solid phase two promethazine molecules with their N,N donor sites encompass the metal. Mass spectral study on the complex confirms that one of the three chlorides is involved in the coordination. The respective changes in the antihistaminic activity of the drug as a result of complexation has been determined and a possible mechanism is suggested.     

The reduction of putidaredoxin reductase by reduced pyridine nucleotides

Putidaredoxin reductase (PdR), an FAD-containing protein, mediates the transfer of electrons from NADH to putidaredoxin in the cytochrome P-450cam-dependent oxidation of camphor. Using stopped-flow spectrophotometry, reduction of putidaredoxin reductase by NADH (70 microM) at 4 degrees C appeared to be a pseudo-first-order process with a rate constant in excess of 600 s-1. The reduction of putidaredoxin reductase by NADPH was much slower with a second-order rate constant of 530 s-1 M-1 at 4 degrees C. The reduction of the enzyme was monitored at several wavelengths: 455 nm to follow flavin reduction; 700 nm to follow the appearance of the long-wavelength charge-transfer complex; and 513 nm to detect the presence of a semiquinone form of the flavoprotein. There was no apparent semiquinone formation observed during reduction. The charge-transfer complex can be formed in the presence of NAD+, whereas, no charge-transfer band could be detected when PdR was reduced with NADPH. The titration of chemically or NADPH-reduced putidaredoxin reductase with either a stoichiometric or an excess amount of NAD+ resulted in the formation of a charge-transfer complex, indicating that the reduced form of PdR has a high affinity for NAD+ regardless of the method of reduction. The data presented indicate that putidaredoxin reductase is reduced without the formation of semiquinone intermediate and, upon reduction, forms a tight complex with NAD+. The Keq for the reduction of PdR by NADPH is 1.1 and the midpoint potential for this reaction is -317 +/- 5 mV.     

Study of the stability of promethazine enantiomers by liquid chromatography using a vancomycin-bonded chiral stationary phase

Three chiral stationary phases based on macrocyclic antibiotics (teicoplanin, vancomycin and ristocetin A) have been tested for chiral separations of promethazine. The vancomycin phase permits the best, baseline enantioseparation of promethazine, with a mobile phase of a 80:20 (v/v) mixture of methanol with a 1% aqueous triethylamine acetate buffer of pH 4.1 and with the analysis time not exceeding 15 min. The limits of detection amount to 27.5 and 31.0 ng/ml for the earlier and later eluting enantiomers, respectively. This separation system, that also permits a sufficient resolution between the promethazine enantiomers and their degradation products, has further been used for the monitoring of the effects of light, temperature and the promethazine concentration in solution on the stability of methanolic promethazine solutions over a period of 19 days. It has been found that the stability of more concentrated solutions is primarily affected by the temperature, whereas the effects of the temperature and light are comparable with more dilute solutions. After 19 days, a solution of 0.5 mg/ml promethazine stored in darkness at a low temperature still contained 84.0% of the original amount of the enantiomers; this value was 89.6% for a solution with the ten times lower promethazine concentration. If the solutions were stored in darkness but at laboratory temperature, the respective values decreased to 38.1 and 62.6% and for the solutions exposed to light at laboratory temperature they decreased even more to 36.7 and 52.6% of the initial promethazine amount.     

Effects of some tricyclic psychopharmacons and structurally related compounds on motility of Proteus vulgaris.

A simple test for the evaluation of drugs interfering with bacterial motility was established with Proteus vulgaris. With this model, promethazine, 7-hydroxy-chlorpromazine, imipramine, 7,8-dioxochlorpromazine and acridine orange were shown to exert significant motility and swarming inhibitory action on Proteus vulgaris strains at subinhibitory concentrations. Quinidine enhanced the antimotility effect of promethazine. The antimotility effect of promethazine was synergized by proton pump inhibitors omeprazole and abscissic acid, but antagonized by extracellular potassium and sodium ions.     

Effects of some tricyclic psychopharmacons and structurally related compounds on motility ofProteus vulgaris

A simple test for the evaluation of drugs interfering with bacterial motility was established withProteus vulgaris. With this model, promethazine, 7-hydroxy-chlorpromazine, imipramine, 7,8-dioxochlorpromazine and acridine orange were shown to exert significant motility and swarming inhibitory action onProteus vulgaris strains at subinhibitory concentrations. Quinidine enhanced the antimotility effect of promethazine. The antimotility effect of promethazine was synergized by proton pump inhibitors omeprazole and abscissic acid, but antagonized by extracellular potassium and sodium ions.     

Efficacy of promethazine suppositories dispensed to outpatient surgical patients.

Postoperative nausea and vomiting frequently complicate outpatient anesthesia and surgery. The duration of treatment for this complication must occasionally extend beyond discharge from the hospital. In this study, we evaluated the commonly used anti-emetic promethazine for its efficacy in the post-discharge period. Adult outpatient surgical patients who had excessive postoperative nausea and vomiting in the recovery room, or who were at risk for postoperative nausea and vomiting following discharge were given two promethazine suppositories (25 mg) for home use. All patients were contacted by our recovery room nurses on the first business day after their surgery and questioned as to their use of the suppositories and, if used, their efficacy. We found that 55 percent of patients given promethazine suppositories for home use had nausea and vomiting in the post-discharge period. Of the patients given promethazine, 89 percent used the suppositories. All of these patients reported improvement in their symptoms following use of the suppositories. None reported adverse effects from the promethazine suppositories. In conclusion, we found promethazine suppositories to be an inexpensive and efficacious treatment for nausea and vomiting in adult outpatient surgical patients following discharge from the hospital. Side-effects were minimal, and our patients voiced no complaints about this mode of therapy. We recommend this therapy for treatment of nausea and vomiting after hospital discharge following adult outpatient surgery.     

The kinetics of complex formation of tryptophan containing proteins with pyridinium salts

Upon preincubation with urea, various 3- or 4-substituted N-methylpyridinium salts form charge-transfer complexes with tryptophan containing proteins such as, L-chymotrypsin and lysozyme. The complexes were studied by using the difference spectrophotometric technique. The fluorescence examination showed that tryptophyl residues in protein molecules are engaged in the complex formation process. The complex formation reactions proceed at a considerable rate. The stopped-flow method was used to determine the pseudo first order rate constants. A linear dependence of the pseudo first order rate constants with the donor concentration was found. The second order rate constants were obtained by dividing the mean value of the pseudo first order rate constants by the initial donor concentration for each run. The linear dependence of second order rate constants with the electron affinity of the acceptors can serve as a criterion for the formation of charge-transfer complexes.     

Retrograde tracing of neural pathways with a protein-gold complex

Summary In this study I have used a tracer complex made of wheat germ agglutinin horseradish peroxidase conjugate (WGA*HRP) coupled to colloidal gold for retrograde tracing of neuronal pathways at the light microscopic level. Visualization of the gold was achieved by silver precipitation (the gold silver intensification method) with gold particles acting as specific cores of nucleation. The presence of horseradish peroxidase in the protein conjugate allowed this method to be compared with classical histochemistry using tetramethylbenzidine as a chromogen. The gold silver intensification method proved to be reliable, specific and sensitive. It has been demonstrated to be useful with fixatives containing a high percentage of paraformaldehyde and compatible with histochemical procedures to show projections of transmitter specific pathways.     

Retrograde tracing of neural pathways with a protein-gold complex. I. Light microscopic detection after silver intensification

In this study I have used a tracer complex made of wheat germ agglutinin horseradish peroxidase conjugate (WGA*HRP) coupled to colloidal gold for retrograde tracing of neuronal pathways at the light microscopic level. Visualization of the gold was achieved by silver precipitation (the gold silver intensification method) with gold particles acting as specific cores of nucleation. The presence of horseradish peroxidase in the protein conjugate allowed this method to be compared with classical histochemistry using tetramethylbenzidine as a chromogen. The gold silver intensification method proved to be reliable, specific and sensitive. It has been demonstrated to be useful with fixatives containing a high percentage of paraformaldehyde and compatible with histochemical procedures to show projections of transmitter specific pathways.     

Interaction of phenols with old yellow enzyme. Physical evidence for charge-transfer complexes.

Evidence is presented that the changes in absorption spectrum obtained on complex formation between Old Yellow Enzyme and phenolic compounds are due to charge-transfer interactions. The positive correlation between the energy of the long wavelength transition and the Hammett para constant with a series of para-substituted phenols indicates that the phenol is the charge-transfer donor and the oxidized flavin of the enzyme is the charge-transfer acceptor. The same conclusion is drawn from studies in which the flavin of the native enzyme, flavin mononucleotide, was replaced by a variety of artificial flavins of different oxidation-reduction potential. The effect of pH on the dissociation constant for the enzyme-ligand binding also indicates that it is the phenolate anion, rather than the conjugate acid, which is responsible for the charge-transfer interaction. The significance of these results is discussed relative to long wavelength absorbing species detected with other flavoproteins.     

Monomeric sarcosine oxidase: role of histidine 269 in catalysis

Conservative mutation of His269 (to Asn, Ala, or Gln) does not-significantly affect the expression of monomeric sarcosine oxidase (MSOX), covalent flavinylation, the physicochemical properties of bound FAD, or the overall protein structure. Turnover with sarcosine and the limiting rate of the reductive half-reaction with L-proline at pH 8.0 are, however, nearly 2 orders of magnitude slower than that with with wild-type MSOX. The crystal structure of the His269Asn complex with pyrrole-2-carboxylate shows that the pyrrole ring of the inhibitor is displaced as compared with wild-type MSOX. The His269 mutants all form charge-transfer complexes with pyrrole-2-carboxylate or methylthioacetate, but the charge-transfer bands are shifted to shorter wavelengths (higher energy) as compared with wild-type MSOX. Both wild-type MSOX and the His269Asn mutant bind the zwitterionic form of L-proline. The E(ox).L-proline complex formed with the His269Asn mutant or wild-type MSOX contains an ionizable group (pK(a) = 8.0) that is required for conversion of the zwitterionic L-proline to the reactive anionic form, indicating that His269 is not the active-site base. We propose that the change in ligand orientation observed upon mutation of His269 results in a less than optimal overlap of the highest occupied orbital of the ligand with the lowest unoccupied orbital of the flavin. The postulated effect on orbital overlap may account for the increased energy of charge-transfer bands and the slower rates of electron transfer observed for mutant enzyme complexes with charge-transfer ligands and substrates, respectively.     

Electronic structures of intermolecular charge-transfer states in fast electron transfers with tetrathiafulvalene donor. Thermal and photoactivation of [2 + 4] cycloaddition to o-chloranil acceptor.

Tetrathiafulvalene () spontaneously forms a series of unusual charge-transfer complexes with various quinonoid acceptors such as o-chloranil () that show pronounced near-IR absorption (lambda(CT) = 1100 nm). The successful isolation of the corresponding [1 : 1] donor-acceptor complex from solution and X-ray crystallographic analysis at low temperatures reveal the polarized charge-transfer state: [(q+),(q-)] with high degree of charge-tranfer (q = 0.6), which is spectrally and crystallographically distinguished from the separate redox (ion-pair) state: [(+) + (-) ]. The unique interconversion of charge-transfer and electron-transfer states is theoretically well-accommodated by Mulliken theory using semi-empirical valence-bond and molecular-orbital methodologies. Mechanistic implications are discussed of both the thermally activated and the photochemically promoted processes via fast (intracomplex) electron transfer followed by collapse of the adiabatic and the non-adiabatic (vibrationally-excited) ion-pairs, respectively, to the [2 + 4] cycloadduct of tetrathiafulvalene and o-chloranil.     

The horseradish peroxidase-catalyzed oxidation of 3,5,3',5'-tetramethylbenzidine. Free radical and charge-transfer complex intermediates

Benzidine and related compounds are well known substrates for horseradish peroxidase/H2O2 oxidation. Typically, two different colored products are formed. In this paper, we study the oxidation of 3,5,3',5'-tetramethylbenzidine. The first colored product is a blue charge-transfer complex of the parent diamine and the diimine oxidation product. This species exists in rapid equilibrium with the radical cation. The radical was observed by ESR spectroscopy, and hyperfine splitting constants were determined. Addition of equimolar hydrogen peroxide yields the yellow diimine, which is stable at acid pH. At less than equimolar peroxide, all four species (diamine, radical cation, charge-transfer complex, and diimine) exist in equilibrium. A theoretical analysis of this redox system is presented, including a determination of the extinction coefficients and equilibrium constant for the nonradical species.     

Retrograde tracing of neural pathways with a protein gold complex. II. Electron microscopic demonstration of projections and collaterals

This paper describes a sensitive method for tracing neural connections at the electron microscopic (EM) level using a new compound produced through the coupling of colloidal gold particles to a wheat germ agglutinin horseradish peroxidase conjugate (the WGA*HRP-gold complex). Visualization of retrogradely labeled cells at the EM level was achieved either directly by gold particles scanning or after silver enhancement. By using different sizes of gold particles individually coupled to WGA*HRP and injected in different brain areas EM detection of multiple retrograde labeling was possible. Thus retrogradely labeled cells were first identified at the light microscopic level through HRP histochemistry with tetramethylbenzidine as a chromogen and then examined under the electron microscope after osmication and embedding. Gold particles were readily identified as electron dense, round dots in spherical grey vesicles. Identification of different sizes of gold particles often localized in the same vesicle established that the protein-gold complex can be used to study collateralisation of parental axons.     

Rapid tranquillisation in psychiatric emergency settings in India: pragmatic randomised controlled trial of intramuscular olanzapine versus intramuscular haloperidol plus promethazine

Objective To compare the effect of intramuscular olanzapine with intramuscular haloperidol plus promethazine on rapid tranquillisation of agitated or violent people with mental illness.Design Pragmatic, allocation concealed, randomised controlled trial.Setting Emergency services of a general hospital psychiatry department in Vellore, south India.Participants 300 adults with agitated or violent behaviour as a result of mental illness; 150 randomised to intramuscular olanzapine and 150 randomised to intramuscular haloperidol plus promethazine.Interventions Open treatment with intramuscular olanzapine or intramuscular haloperidol plus promethazine.Main outcome measures Primary outcome was proportion of patients who were tranquil or asleep at 15 minutes and 240 minutes. Secondary outcomes were proportion of patients who were tranquil, asleep, restrained, absconding, or clinically improved at 15, 30, 60, 120, and 240 minutes; additional medical interventions and adverse effects over four hours; and compliance with oral drugs and adverse effects over two weeks.Results Of 300 people randomised to receive either intramuscular olanzapine or intramuscular haloperidol plus promethazine, follow-up data were available for primary outcomes for 298 (99%). Both treatments resulted in similar proportions of people being tranquil or asleep at 15 minutes (olanzapine 131/150 (87%), haloperidol plus promethazine 136/150 (91%); relative risk 0.96, 95% confidence interval 0.34 to 1.47) and 240 minutes (olanzapine 144/150 (96%), haloperidol plus promethazine 145/150 (97%); relative risk 0.99, 0.95 to 1.03). However, more people given olanzapine than those given haloperidol plus promethazine required additional drugs over four hours (65/150 (43%) v 31/150 (21%); relative risk 2.07, 1.43 to 2.97). Adverse effects were uncommon with both treatments.Conclusions Intramuscular olanzapine and intramuscular haloperidol plus promethazine were effective at rapidly tranquillising or sedating agitated or violent patients with mental illness but the combination resulted in fewer additional medical interventions within four hours of intervention.Trial registration Clinical trials {"type":"clinical-trial","attrs":{"text":"NCT00455234","term_id":"NCT00455234"}}NCT00455234.     

Physicochemical properties of charge-transfer complexes of plastoquinone and alpha-tocopherol quinone, and their possible role in vivo

It has been found that the solubility of PQH2 and alpha-TQH2 in hexane increased with the increase in PQ and alpha-TQ concentrations, respectively, that is connected with the formation of quinhydrone-type charge-transfer complexes. Measurements of the solubility of both prenylquinones and their reduced forms in hexane and acetone, at -30 degrees C and room temperature, showed a much higher affinity of the quinol forms for acetone than for hexane. In the case of quinones, the difference in affinity was not significant. The possibility of charge-transfer complex formation by PQ and alpha-TQ in thylakoid membranes and the influence of such complexes on the diffusion of PQH2 and alpha-TQH2 molecules have been considered.     

Promethazine improves antibiotic efficacy and disrupts biofilms of Burkholderia pseudomallei

Efflux pumps are important defense mechanisms against antimicrobial drugs and maintenance of Burkholderia pseudomallei biofilms. This study evaluated the effect of the efflux pump inhibitor promethazine on the structure and antimicrobial susceptibility of B. pseudomallei biofilms. Susceptibility of planktonic cells and biofilms to promethazine alone and combined with antimicrobials was assessed by the broth microdilution test and biofilm metabolic activity was determined with resazurin. The effect of promethazine on 48 h-grown biofilms was also evaluated through confocal and electronic microscopy. The minimum inhibitory concentration (MIC) of promethazine was 780 mg l^?1, while the minimum biofilm elimination concentration (MBEC) was 780–3,120 mg l^?1. Promethazine reduced the MIC values for erythromycin, trimethoprim/sulfamethoxazole, gentamicin and ciprofloxacin and reduced the MBEC values for all tested drugs (p<0.05). Microscopic analyses demonstrated that promethazine altered the biofilm structure of B. pseudomallei, even at subinhibitory concentrations, possibly facilitating antibiotic penetration. Promethazine improves antibiotics efficacy against B. pseudomallei biofilms, by disrupting biofilm structure.     

Pleiotropic impact of a single lysine mutation on biosynthesis of and catalysis by N-methyltryptophan oxidase

N-Methyltryptophan oxidase (MTOX) contains covalently bound FAD. N-Methyltryptophan binds in a cavity above the re face of the flavin ring. Lys259 is located above the opposite, si face. Replacement of Lys259 with Gln, Ala, or Met blocks (>95%) covalent flavin incorporation in vivo. The mutant apoproteins can be reconstituted with FAD. Apparent turnover rates (k(cat,app)) of the reconstituted enzymes are ~2500-fold slower than those of wild-type MTOX. Wild-type MTOX forms a charge-transfer E(ox)·S complex with the redox-active anionic form of NMT. The E(ox)·S complex formed with Lys259Gln does not exhibit a charge-transfer band and is converted to a reduced enzyme·imine complex (EH(2)·P) at a rate 60-fold slower than that of wild-type MTOX. The mutant EH(2)·P complex contains the imine zwitterion and exhibits a charge-transfer band, a feature not observed with the wild-type EH(2)·P complex. Reaction of reduced Lys259Gln with oxygen is 2500-fold slower than that of reduced wild-type MTOX. The latter reaction is unaffected by the presence of bound product. Dissociation of the wild-type EH(2)·P complex is 80-fold slower than k(cat). The mutant EH(2)·P complex dissociates 15-fold faster than k(cat,app). Consequently, EH(2)·P and free EH(2) are the species that react with oxygen during turnover of the wild-type and mutant enzyme, respectively. The results show that (i) Lys259 is the site of oxygen activation in MTOX and also plays a role in holoenzyme biosynthesis and N-methyltryptophan oxidation and (ii) MTOX contains separate active sites for N-methyltryptophan oxidation and oxygen reduction on opposite faces of the flavin ring.