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PubMedDate not supplied

Identification of major urinary metabolites of the catechol-O-methyltransferase inhibitor entacapone in the dog.

Metabolites of entacapone, (E)-2-cyano-N,N-diethyl-3-(3,4-dihydroxy-5-nitrophenyl) propenamide, a potent inhibitor of catechol-O-methyltransferase, were isolated from dog urine. After hydrolysis of glucuronides and sulfates, 5 metabolites were identified in addition to unchanged entacapone by HPLC with diode-array UV detection, electron ionization mass spectrometry and IR spectroscopy. The (Z)-isomer of entacapone was the most abundant phase I metabolite while less abundant metabolites were formed through cleavage or reduction of the side chain carbon-carbon double bond, hydrolysis of the amide bond or through hydration of the nitrile group. The most abundant urinary metabolites were glucuronides. The glucuronidation site of these ortho-nitrocatechols was shown to be the hydroxyl meta to the nitro group.

Animals↗
PubMed2000

Spectroscopy of aqueous solutions: protein and DNA interactions with water.

This review emphasises the need to use spectroscopy in order to understand the behaviour of water, and summarises the background of the subject. The various forms of spectroscopy that are especially informative are described, with particular reference to near-infrared (NIR) spectrophotometry. The key results are outlined, first those obtained with small molecules and ions, and second those involving proteins, DNA and cell membranes. Finally, some interpretations are offered which include the novel but possibly controversial concept of free OH and free lone-pair groups.

Cell Membrane↗
PubMed2003

Comparison of three spectrophotometric methods for the determination of gamma-oryzanol in rice bran oil.

A comparison of the results obtained by applying three spectrophotometric methods (at fixed wavelength, second-derivative and multicomponent analysis) to the determination of gamma-oryzanol in rice bran oil is reported. At fixed wavelength the results are more accurate when using isopropyl alcohol, rather than n-heptane, to dilute the oil samples, because the absorption bands of gamma-oryzanol are red-shifted and the absorbance, measured at lambda(max)=327 nm, is less affected by the interference of the oil "matrix" (lambda(max)=314 nm in n-heptane).However, to obtain accurate results also in oils with a low content of gamma-oryzanol, it is necessary to perform the analysis using second-derivative ((2)D330.365) or multicomponent (lambda=310-360 nm) methods. The first one fully removes the interference of oil matrix whilst the second, which needs a specific computational program to process the spectrophotometric data, furnishes evidence the presence of some unexpected interference in the analysis and/or standards which are not representative of the analysed samples, from the square root of the sum of the squared differences at each point between the linear combination of the standards and the unknown spectra (RMS error).Finally, some aspects of the chemical, spectroscopic (UV, IR) and thermoanalytical (TG, DSC) behaviour of gamma-oryzanol and the values of the parameters which enable "computation" of its UV spectra are reported.

Hot Temperature↗
PubMed2003

The chromatographic behavior of group (IIB) metal ions on polyurethane foam functionalized with 8-hydroxyquinoline.

Polyurethane foam functionalized with 8-hydroxyquinoline has been prepared by coupling the foam matrix with 8-hydroxyquinoline (oxine) through an azo spacer. The oxine-bonded foam (Ox PUF) was characterized by use of different tools (UV-Vis spectra, IR spectra, density, and stability). Ox PUF was found to be very suitable for separation and preconcentration of trace metals, e.g. Zn(II), Cd(II), and Hg(II) ions, from wastewater in the pH ranges 2-12, 9-12, and 3-6, respectively. Various conditions influencing the sorption of these metal ions on to Ox PUF were optimized. Extraction of the metal ions was accomplished in 15 to 20 min. Study of the variation of the sorption of the tested metal ions with temperature yielded average values for DeltaH, DeltaS, and DeltaG of 41.99, 158.23, and -5.1 kJ mol(-1), respectively. The capacities of the foam material were 0.27, 0.16, and 0.09 mmol g(-1) for Zn(II), Cd(II), and Hg(II), respectively. Preconcentration factors >50 were achieved (RSD approximately 6.18). The quantitative results were obtained from experiments performed using certified reference materials.

Cadmium↗
PubMed2005

Multivariate curve resolution: a method of evaluating the kinetics of biotechnological reactions.

In biotechnology, strong emphasis is placed on the development of wet chemical analysis and chromatography to separate target components from a complex matrix. In bioprocessing, the development of single compound biosensors is an important activity. The advantages of these techniques are their high sensitivity and specificity. Inline or online monitoring by means of spectroscopy has the potential to be used as an "all-in-one" analysis technique for biotechnological studies, but it lacks specificity. Multivariate curve resolution (MCR) can be used to overcome this limitation. MCR is able to extract the number of components involved in a complex spectral feature, to attribute the resulting spectra to chemical compounds, to quantify the individual spectral contributions, and to use this quantification to develop kinetic models for the process with or without a priori knowledge. After a short introduction to MCR, two applications are presented. In the first example, the spectral features of hemp are monitored and analysed during growth. MCR provides unperturbed spectra on the activity of, for example, lignin and cellulose during plant development. In a second example, the kinetics of a laccase enzyme-catalysed degradation of aromatic hydrocarbons are calculated from UV/VIS spectra.

Biotechnology↗
PubMed2000

A calix[4]arene based calcium-selective optode membrane: measuring the absorbance maximum wavelength shift.

An absorbance based calcium ion sensor is presented which applies a new immobilized chromogenic calix[4]arene. The membrane consists of a hydrogel/1,3-pentanedial mixture and the 1,3-bis(indoaniline)-derived 2,4-bis-[(ethylcarbonyl)methoxyl-calix[4]arene as calcium receptor. The indicator entrapped within the gel was not rapidly washed out. Upon calcium complexation a bathochromic shift up to 70 nm was observed along with an increase of the absorption coefficient. The dynamic range of calcium measurements is from 3 to 10 mM with a point of inflection of the calibration curve at a calcium concentration of about 7 mM. The concentration of calcium ions can be calculated from either absorbance at a distinct wavelength or--preferably when indicator leaching occurs--from the wavelength shift of the absorbance occurring when calcium levels are increased.

Calcium↗
PubMed2002

Changes in cerebral haemodynamics, regional oxygen saturation and amplitude-integrated continuous EEG during hypoxia-ischaemia and reperfusion in newborn piglets.

Perinatal asphyxia models are necessary to obtain knowledge of the pathophysiology of hypoxia-ischaemia (HI) and to test potential neuroprotective strategies. The present study was performed in newborn piglets to obtain information about simultaneous changes in cerebral oxygenation and haemodynamics and electrocortical brain activity during a 60-min period of HI and up to 2 h of reperfusion using near infrared spectrophotometry (NIRS) and the amplitude-integrated EEG (aEEG). HI was induced by occluding both carotid arteries and decreasing the fraction of inspired oxygen (FiO(2)) to 0.08-0.12 for 60 min. The mean arterial blood pressure (MABP) and heart rate increased, the oxygenated haemoglobin (O(2)Hb) decreased, and the deoxygenated haemoglobin (HHb) increased, but total haemoglobin (tHb) remained stable during the 60-min HI period. The regional oxygen saturation (rSO(2)) was significantly decreased during the whole HI period, as was the electrocortical brain activity. Upon reperfusion and reoxygenation, the MABP normalised to baseline values but the heart rate remained increased. O(2)Hb and HHb recovered to baseline values and tHb remained unchanged. As indicated by the unchanged tHb values during the HI period, it was suggested that compensatory cerebral perfusion occurred during this period, probably via the vertebrobasilar arterial system. Furthermore, in this model a clear hyperperfusion period directly upon reperfusion and reoxygenation is not present. rSO(2) showed a quick recovery to baseline values, but the aEEG-measured electrocortical brain activity remained reduced following HI. In conclusion, the rSO(2) and aEEG showed a different time profile following perinatal asphyxia. The stable tHb during HI and reperfusion in this model differs from observations in human neonates.

Animals↗
PubMed2002

Pharmacological interventions in the newborn piglet in the first 24 h after hypoxia-ischemia. A hemodynamic and electrophysiological perspective.

The purpose of this study was to investigate whether combined inhibition of neuronal and inducible nitric oxide synthase (NOS) by 2-iminobiotin, free radical scavenging by allopurinol, and non-protein-bound iron chelation with deferoxamine improved cerebral oxygenation, electrocortical brain activity, and brain energy status during the first 24 h after hypoxia-ischemia (HI) in the newborn piglet. Forty-three newborn piglets were subjected to 1 h of severe HI by occluding both carotid arteries and phosphorous magnetic resonance spectroscopy ((31)P-MRS)-guided hypoxia, whereas five served as sham-operated controls. Upon reperfusion, piglets received vehicle (n=12), 2-iminobiotin (n=11), allopurinol (n=10), or deferoxamine (n=10). Cerebral oxygenation was recorded with near-infrared spectrophotometry (NIRS), electrocortical brain activity was assessed with amplitude-integrated EEG (aEEG), and cerebral energy status with (31)P-MRS. The oxygenated hemoglobin (HbO(2)) and total hemoglobin (tHb) were significantly increased in vehicle-treated piglets compared with 2-iminobiotin-treated and deferoxamine-treated piglets. No change in deoxygenated Hb (HHb) was demonstrated over time. The aEEG was significantly preserved in 2-iminobiotin- and deferoxamine-treated piglets compared with vehicle-treated piglets. Allopurinol treatment was not as effective as 2-iminobiotin treatment after HI. Phosphocreatine/inorganic phosphate ratios (PCr/P(i)) were significantly decreased for vehicle-treated piglets at 24 h post-HI, whereas 2-iminobiotin, allopurinol, and deferoxamine prevented the development of secondary energy failure. We speculate that the beneficial effects, especially of 2-iminobiotin, but also of deferoxamine, are due to reduced peroxynitrite-mediated oxidation.

Allopurinol↗
PubMedDate not supplied

Cerebral oxygenation in children with syncope during head-upright tilt test.

The pathophysiology of neurocardiogenic syncope remains incompletely known. In this entity, besides abnormal systemic hemodynamic regulation, potential cerebral circulatory abnormalities have been reported. In this setting, cerebral saturation assessment could detect cerebral blood flow changes and estimate the sufficiency of brain oxygenation during the event. A head-upright tilt test was performed in 25 children aged between 6 and 16 years. In addition to the standard protocol, cerebral oxygen saturation was determined noninvasively by means of a near-infrared spectrophotometry device. In the 19 children with a positive tilt test, significant impairment of cerebral saturation was detected both at the start of the patient's complaints (without hemodynamic modifications) and during syncope. Our results support the hypothesis of the presence of abnormal cerebral hemodynamic autoregulation in children with neurocardiogenic syncope.

Adolescent↗
PubMed2001

Model investigations for vanadium-protein interactions: vanadium(III) compounds with dipeptides and their oxovanadium(IV) analogues.

The reaction of VCl(3) with 1,10-phenanthroline and a series of dipeptides (H(2)dip), having aliphatic as well as aromatic side chains, in methyl alcohol and in the presence of triethylamine affords vanadium(III) compounds of the general formula [V(III)(dip)(MeOH)(phen)]Cl. Aerial oxidation/hydrolysis of the vanadium(III) species gives their oxovanadium(IV) analogues of the general formula [V(IV)O(dip)(phen)]. X-ray crystallographic characterization of the [V(IV)O(dip)(phen)] compounds (where dip(2-)=Gly- L-Ala, Gly- L-Val and Gly- L-Phe) revealed that the vanadium atom possesses a severely distorted octahedral coordination and is ligated to a tridentate dip(2-) ligand at the N(amine) atom, the deprotonated N(peptide) atom and one of the O(carboxylate) atoms, as well as an oxo group and two phenanthroline nitrogen atoms. Circular dichroism characterization of the V(III)/V(IV)O(2+)-dipeptide compounds revealed a strong signal for the V(IV)O(2+) species in the visible range of the spectrum, with a characteristic pattern which may be exploited to identify the N(am), N(pep) and O(car) ligation of a peptide or a protein to V(IV)O(2+) center, and a weak Cotton effect of opposite sign to their vanadium(III) analogues. The visible spectra of the V(III)-dipeptide compounds revealed two d-d bands with high intensity, thus indicating that the covalency of the metal-donor atoms is significant, i.e. the vanadium d orbitals are significantly mixed with the ligand orbitals, and this is confirmed by the low values of their Racah B parameters. The high-intensity band of the V(IV)O(2+)-dipeptide compounds at approximately 460 nm implies also a strong covalency of the metal with the equatorial donor atoms and this was supported by the EPR spectra of these compounds. Moreover, the V(III)/V(IV)O(2+)-dipeptide complexes were characterized by EPR and IR spectroscopies as well as conductivity and magnetic susceptibility measurements.

Circular Dichroism↗
PubMed2003

Spectroscopic characterization of the [Fe(His)(4)(Cys)] site in 2Fe-superoxide reductase from Desulfovibrio vulgaris.

The electronic and vibrational properties of the [Fe(His)(4)(Cys)] site (Center II) responsible for catalysis of superoxide reduction in the two-iron superoxide reductase (2Fe-SOR) from Desulfovibrio vulgaris have been investigated using the combination of EPR, resonance Raman, UV/visible/near-IR absorption, CD, and VTMCD spectroscopies. Deconvolution of the spectral contributions of Center II from those of the [Fe(Cys)(4)] site (Center I) has been achieved by parallel investigations of the C13S variant, which does not contain Center I. The resonance Raman spectrum of ferric Center II has been assigned based on isotope shifts for (34)S and (15)N globally labeled proteins. As for the [Fe(His)(4)(Cys)] active site in 1Fe-SOR from Pyrococcus furiosus, the spectroscopic properties of ferric and ferrous Center II in D. vulgaris 2Fe-SOR are indicative of distorted octahedral and square-pyramidal coordination geometries, respectively. Differences in the properties of the ferric [Fe(His)(4)(Cys)] sites in 1Fe- and 2Fe-SORs are apparent in the rhombicity of the S=5/2 ground state ( E/ D=0.06 and 0.28 in 1Fe- and 2Fe-SORs, respectively), the energy of the CysS(-)(p(pi))-->Fe(3+)(d(pi)) CT transition (15150+/-150 cm(-1) and 15600+/-150 cm(-1) in 1Fe- and 2Fe-SORs, respectively) and in changes in the Fe-S stretching region of the resonance Raman spectrum indicative of a weaker Fe-S(Cys) bond in 2Fe-SORs. These differences are interpreted in terms of small structural perturbations in the Fe coordination sphere with changes in the Fe-S(Cys) bond strength resulting from differences in the peptide N-H.S(Cys) hydrogen bonding within a tetrapeptide bidentate "chelate". Observation of the characteristic intervalence charge transfer transition of a cyano-bridged [Fe(III)-NC-Fe(II)(CN)(5)] unit in the near-IR VTMCD spectra of ferricyanide-oxidized samples of both P. furiosus 1Fe-SOR and D. vulgaris 2Fe-SOR has confirmed the existence of novel ferrocyanide adducts of the ferric [Fe(His)(4)(Cys)] sites in both 1Fe- and 2Fe-SORs.

Binding Sites↗
PubMed2006

Stereoselective and driving-force-dependent photoinduced electron-transfer reactions of zinc myoglobin with optically active N,N'-dimethylcinchoninium and N,N'-dimethylcinchonidinium ions.

In order to understand the detailed mechanism of the stereoselective photoinduced electron-transfer (ET) reactions of zinc-substituted myoglobin (ZnMb) with optically active molecules by flash photolysis, we designed and prepared new optically active agents, such as N,N'-dimethylcinchoninium diiodide ([MCN]I2) and N,N'-dimethylcinchonidinium diiodide ([MCD]I2). The photoexcited triplet state of ZnMb, 3(ZnMb)*, was successfully quenched by [MCN]2+ and [MCD]2+ ions to form the radical pair of ZnMb cation (ZnMb.+) and reduced [MCN].+ and [MCD].+, followed by a thermal back ET reaction to the ground state. The rate constants (kq) for the ET quenching at 25 degrees C were obtained as kq(MCN)=(1.9+/-0.1)x10(6) M-1 s-1 and kq(MCD)=(3.0+/-0.2)x10(6) M-1 s-1, respectively. The ratio of kq(MCD)/kq(MCN)=1.6 indicates that the [MCD]2+ preferentially quenches 3ZnMb)*. The second-order rate constants (kb) for the thermal back ET reaction from [MCN].+ and [MCD].+ to ZnMb.+ at 25 degrees C were kb(MCN)=(0.79+/-0.04)x10(8) M-1 s-1 and kb(MCD)=(1.0+/-0.1)x10(8) M-1 s-1, respectively, and the selectivity was kq(MCD)/kq(MCN)=1.3. Both quenching and thermal back ET reactions are controlled by the ET step. In the quenching reaction, the energy differences of DeltaDeltaH ( not equal)(MCD-MCN) and DeltaDeltaS ( not equal)(MCD-MCN) at 25 degrees C were obtained as -1.1 and 0 kJ mol-1, respectively. On the other hand, DeltaDeltaH (not equal)(MCD-MCN)=11+/-2 kJ mol-1 and TDeltaDeltaS (not equal)(MCD-MCN)=-10+/-2 kJ mol-1 were given in the thermal back ET reaction. The highest stereoselectivity of 1.7 for [MCD].+ found at low temperature (10 degrees C) was due to the DeltaDeltaS ( not equal) value obtained in the thermal back ET reaction.

Cinchona Alkaloids↗
PubMed2006

Oxoiron(IV) complexes of the tris(2-pyridylmethyl)amine ligand family: effect of pyridine alpha-substituents.

The oxoiron(IV) complexes of two 6-substituted tris(2-pyridylmethyl)amine ligand derivatives have been generated and characterized with respect to their spectroscopic and reactivity properties. The introduction of an alpha-substituent maintains the low-spin nature of the oxoiron(IV) unit but weakens the ligand field, as evidenced by red shifts in its characteristic near-IR chromophore. While its hydrogen-atom abstraction ability is only slightly affected, the oxo-transfer reactivity of the oxoiron(IV) center is significantly enhanced relative to that of the parent complex. These results demonstrate that the ligand environment plays a key role in modulating the reactivity of this important biological oxidant.

Iron Compounds↗
PubMed2005

Rhodestrin: a novel indole terpenoid phytohormone from Rhodobacter sphaeroides.

A new phytohormone was isolated as a metabolite of anthranilate photobiotransformation by Rhodobacter sphaeroides OU5. It was identified by MS and NMR ((1)H, (13)C) as an indole terpenoid ester [(2E,4E,6E,8E,10E,12E,14E,16E,18E)24-hydroxy-2,6,10,14,19 pentamethyl tetrecosa-2,4,6,8,10,12,14,16,18 nonenyl-2(hydroxy methyl)-1H-indole-3-carboxylate] and is named as rhodestrin. Rhodestrin at 50 nM: gave positive test in auxin bioassay and initiated more profuse and early rooting in tissue-cultured plants than other auxins at 5 microM.

Biotransformation↗
PubMed1997

Synthesis and nuclear magnetic resonance properties of all geometrical isomers of conjugated linoleic acids.

Pure geometric isomers of conjugated linoleic acid were prepared from castor oil as the primary starting material. Methyl octadeca-9Z,11E-dienoate (2) and methyl octadeca-9Z,11Z-dienoate (4) were obtained by zinc reduction of methyl santalbate (1, methyl octadec-11E-en-9-ynoate) and methyl octadec-11Z-en-9-ynoate (3), respectively, as the key intermediates. Methyl octadeca-9E,11E-dienoate (8) and methyl octadeca-9E,11Z-dienoate (9) were prepared by demesylation of the mesyloxy derivative of methyl ricinelaidate (6, methyl 12-hydroxy-octadec-9E-enoate). A study of the nuclear magnetic resonance spectral properties was carried-out, and the shifts of the olefinic carbon atoms of 18:2(9Z,11E) (2) and 18:2(9E,11Z) (9) were readily identified by a combination of incredible natural abundance double quantum transfer experiment, heteronuclear multiple bond correlation, and 1H-13C correlation spectroscopy correlation techniques. Doubts remain in the absolute identification of the individual olefinic carbon atoms of the 18:2(9Z,11Z) (4) and 18:2(9E,11E) (8), except the fact that the shifts of the "inner" (C-10 and C-11) and "outer" (C-9 and C-12) positioned olefinic carbon atoms of the conjugated diene system are distinguishable.

Isomerism↗
PubMed1981

Idiopathic familial chondrocalcinosis due to apatite crystal deposition.

Idiopathic familial chondrocalcinosis was found in five members of a family. The clinical features of the disease were morning stiffness, pain and limitation of motion of the dorsolumbar spine in four of the five members, associated with arthritis of the small joints of the hands in three, shoulder periarthritis in two and costal cartilage pain in one. Radiologically, four of the five patients had multiple intervertebral disk calcifications, mainly located at the nucleus pulposus area. Three of them also had periarticular calcific deposits, associated with costal cartilage calcifications and degenerative changes in the small joints of the hands in two. None of these cases showed cartilage calcification in the knees, public symphysis or triangular ligament of carpus. In the propositus, optical microscopy of a specimen of the second proximal interphalangeal joint obtained by open biopsy showed the presence of multiple calcified areas in the intercellular matrix and chondroid metaplasia with calcification of the matrix in the synovial membrane and capsule. X-ray diffraction studies, energy dispersive analysis, and infrared spectrophotometry of a costal cartilage sample obtained by open biopsy demonstrated the presence of carbonate calcium hydroxyapatite. In this study, no relation was found between HLA antigens, loci A, B and C, and this syndrome due to calcium hydroxyapatite crystal deposition.

Adult↗