Determination of polyhydroxyalkanoates in activated sludge by ion chromatographic and enzymatic methods

Two new detection methods for the determination of poly-beta-hydroxybutyrate (PHB) and -valerate (PHV) are described. Both methods are based on depolymerization of PHB/PHV to 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV). Depolymerization was achieved by either propanolic or hydrolytic digestion. Propanolic digestion transformed commercial PHB/PHV stoichiometrically into 3HB/3HV and yielded apparently complete recoveries of bacterial PHB/PHV from activated sludge. Hydrolytic digestion was suitable only for PHB determination. For quantification of 3HB and 3HV directly from digested sludge, a method based on ion-exchange chromatography and conductivity detection was developed (IC-method). Alternatively, the total of 3HB and 3HV was quantified using a commercial enzymatic test kit and colorimetric detection (enzyme method). Both detection methods are easier to perform than previous methods and are suitable for complex matrices such as activated sludge. The IC-method is recommended for high sample throughputs or if distinction between PHB and PHV is essential. Enzymatic detection is recommended if a few samples per day have to be measured immediately or if an ion chromatograph is unavailable.

n-Propanol as a substrate for assaying the ligninperoxidase activity of Phanerochaete chrysoporium

The steady state kinetics of ligninperoxidase catalysed reaction using n-propanol as the organic substrate and monitoring the formation of propanaldehyde at lambda = 300 nm spectrophotometerically as functions of different reaction parameters has been studied. It has been concluded that n-propanol can be used as a substrate for analysing the activity of ligninperoxidase. The turnover number of ligninperoxidase of Phanerochaete chrysosporium using n-propanol as substrate has been found to be higher approximately by a factor of 10(3) as compared to that using veratryl alcohol as the substrate. The method works in assaying the activity of ligninperoxidase produced by Aspergillus fumigatus indicating that it can be used for assaying the ligninperoxidase activities produced by other microorganisms also and is not limited to assaying the ligninase activity produced by Phanerochaete chrysosporium alone. Under identical experimental conditions, horseradish peroxidase does not show peroxidase activity using n-propanol as substrate indicating that the method does not interfere with the activities of other peroxidases.

Quantitation of pyrethrum residues in brown tree snakes

A reversed-phase solid-phase extraction-gas chromatography (SPE-GC)-electron capture detection method is developed to quantitate individual rethrin residues in pyrethrum-exposed brown tree snakes. Aliquots (6 g) of homogenized snake tissue are extracted with 10 mL acetonitrile. The rethrins are recovered from the acetonitrile extract and concentrated using C8 SPE. The rethrins are eluted from the SPE column with pentane, evaporated to near dryness, and reconstituted to 1 mL with 1-propanol. Individual rethrins are quantitated using GC analysis of the 1-propanol solution. Method limits of detection for rethrins range from 0.63 to 6.51 ng/g. The mean recovery for all rethrins is 70.8% with a standard deviation of 5.7%. This method is used to successfully quantitate incurred rethrin residues in pyrethrum-exposed brown tree snakes.

Acoustic measurements in a tissue mimicking liquid

A liquid has been developed that mimics soft tissue in terms of propagation speed, attenuation, and nonlinearity parameter B/A. Since the slope of the attenuation coefficient is nearly constant up to at least 18 MHz and the value can be anywhere in the range 0.1 through 0.7 dB/(cm MHz), the material is ideal for assessing the effectiveness of attenuation derating of output acoustic intensities and pressures measured in water. A clinical ultrasound system was used to transmit into the tissue mimicking liquid. The pulse intensity integral and rarefactional pressure at various field locations in the tissue mimicking liquid were computed and compared to the corresponding values measured in water with attenuation derating applied. The slope of the attenuation coefficient in the tissue mimicking liquid was used for the derating. From this data it is seen that the present practice of modeling in vivo exposure using linearly derated measurements made in water is not always conservative.

Chiral separation of polychlorinated biphenyls by micellar electrokinetic chromatography with sodium cholate

Micellar electrokinetic chromatography (MEKC) with one kind of bile salt (sodium cholate) was used to separate three chiral polychlorinated biphenyls (PCBs; 84, 95, and 176), each one in its two enantiomers. Sodium cholate was used as chiral surfactant in a 2-(N-cyclohexylamino) ethanesulfonic acid (CHES) buffer under alkaline (pH 10) conditions containing urea (2 M). The influence of bile salt concentration on the efficiency and the resolution between the two enantiomers of PCBs 84 and 95 was established. The chiral separation of three PCBs was successfully achieved in less than 30 min (approximately 23 min for PCB 176 and approximately 29 min for PCBs 84 and 95).

Characterization of enzymatic pectin digests by matrix-assisted laser desorption/ionization mass spectrometry

The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the characterization of partially methyl-esterified enzymatic pectin digests is described. The sensitivities of several matrices, positive and negative ion modes and desalting techniques for these acidic oligosaccharides were compared. The most favorable results were obtained with a thin-layer preparation of a mixture of 2,4,6-trihydroxyacetophenone and nitrocellulose in the negative ion mode. Results are presented demonstrating the sensitive characterization of separated and unseparated high-ester pectin digests obtained after complete digestion using Aspergillus niger pectin lyase and the analysis of digests after chemical modification. In the case of unseparated digests, the analysis of methylation patterns is demonstrated. Oligomers with a degree of polymerization up to 40 were detected after enrichment of large oligomers by propan-2-ol precipitation.

Capillary electrophoresis of phospholipids with indirect photometric detection

The capillary electrophoresis (CE) separation of different anionic phospholipid classes including phosphatidic acids (PA), phosphatidylserine, phosphatidylinositol, phosphatidylglycerol (PG), and cardiolipin using indirect detection with adenosine monophosphate (AMP) is described. A standard mixture of PAs (C14, C16, and C18) can be separated in 10 min by CE using 5 mM AMP and 100 mM boric acid in 10% water--80% methanol--10% acetonitrile. Although nonionic surfactants such as Brij 35 can improve the CE resolution of PAs, the separation time and the baseline noise are both increased. Optimization of the organic solvent in the running electrolyte is important. Methanol provides faster electroosmotic flow than propanol, and 10% acetonitrile effectively reduces migration time further by a factor of 1.4-2.2, depending on the phospholipid. The concentration limit of detection ranges from approximately 2 to 6 mg/L, and the mass limit of detection is as low as 21 pg. Linearity from 19 to 100 mg/L is established for cardiolipin and C16-PG. Phospholipids in soybean and brain extract samples could be profiled.

Studies on the permeation of inorganic salts through plastic films

Permeation tests were carried out under several conditions for various metal ions, anions, temperatures and solvents. The study was designed as lag-time experiments where the amount of metal penetrating through the polymer was plotted against time. Diffusion and permeability coefficients were measured using the time-lag technique and by calculating the permeation rate. Graphite furnace atomic absorption spectroscopy was used to quantify the amounts of metal ions. Permeation of inorganic salts through low density polyethylene (LDPE) showed a strong dependency on the solvent used. With water as solvent, no permeation was measurable even at 60 degrees C, while ethanol, 1-propanol and 2-propanol gave increasing permeation. Small amounts of water in pure ethanol diminished the permeation rate considerably. Chloride salts led to the fastest diffusion, whereas bromide salts gave the highest permeation rate. Acetates and nitrates show virtually no permeation. In ethanol, copper chloride permeated faster than iron, zinc, cobalt, nickel or lithium chloride, and only tin chloride diffused faster than copper chloride. Reasons for the observed permeation behaviour are assumed to be the molecular size of an undissociated molecule, the degree of dissociation and the solvation in a solvent.

Conformationally driven protease-catalyzed splicing of peptide segments: V8 protease-mediated synthesis of fragments derived from thermolysin and ribonuclease A

We have studied the conformation as well as V8 protease-mediated synthesis of peptide fragments, namely amino acid residues 295-316 (TC-peptide) of thermolysin and residues 1-20 (S-peptide) of ribonuclease A, to examine whether "conformational trapping" of the product can facilitate reverse proteolysis. The circular dichroism study showed cosolvent-mediated cooperative helix formation in TC-peptide with attainment of about 30-35% helicity in the presence of 40% 1-propanol and 2-propanol solutions at pH 6 and 4 degrees C. The thermal melting profiles of TC-peptide in the above cosolvents were very similar. V8 protease catalyzed the synthesis of TC-peptide from a 1:1 mixture of the non-interacting complementary fragments (TC295-302 and TC303-316) in the presence of the above cosolvents at pH 6 and 4 degrees C. In contrast, V8 protease did not catalyze the ligation of S1-9 and S10-20, although S-peptide could assume helical conformation in the presence of the cosolvent used for the semisynthetic reaction. V8 protease was able to synthesize an analog of S-peptide (SA-peptide) in which residues 10-14 were substituted (RQHMD-->VAAAK). While S-peptide exhibited helical conformation in the presence of aqueous propanol solutions, SA-peptide displayed predominantly beta-sheet conformation. SA-peptide showed enhanced resistance to proteolysis as compared with S-peptide. Thus, failure of semisynthesis of S-peptide may be a consequence of high flexibility around the 9-10 peptide bond due to its proximity to the helix stop signal. The results suggest that protease-mediated ligations may be achieved by design and manipulation of the conformational aspects of the product.

Preferential solvation changes upon lysozyme heat denaturation in mixed solvents

On the basis of scanning microcalorimetry data from literature and our own measurements, we have calculated the changes in preferential solvation of lysozyme upon heat denaturation in six solvent systems: water + methanol, ethanol, propanol [data from Velicelebi, G., & Sturtevant, J. M. (1979) Biochemistry 18, 1180], acetone, p-dioxane [data from Fujita, Y., & Noda, Y. (1983) Bull. Chem. Soc.Jpn. 56, 233], and dimethylsulfoxide [our data Kovrigin, E. L., Kirkitadze, M. D., & Potekhin, S. A. (1996) Biofizika 41, 549-553; Kovrigin, E. L., & Potekhin, S. A. (1996) Biofizika 41, 1201-1206]. These preferential solvation changes are (in effect) the numbers of cosolvent molecules entering or leaving the solvation shell of the protein upon denaturation. It has been shown that for a group of five substances in the initial activity range (approximately up to 0. 3) the denaturational changes of preferential solvation of lysozyme do not depend on the nature of the solvent and depend only on its activity. This suggests that lysozyme does not distinguish these substances in the initial activity range and preferential solvation has a nonspecific character. It has been shown also that preferential solvation DeltaGamma23 does not depend on the pH value at least for dimethylsulfoxide-water solutions. This indicates that the chargeable groups exposed on denaturation do not contribute significantly to preferential interaction of the protein surface with the solution components.

Rapid clinical evaluation of anosmia. The alcohol sniff test

BACKGROUND

Smell impairment affects 1% to 2% of Americans and leads to frequent physician visits. Olfactory testing is available in chemosensory centers, but not as part of a routine cranial nerve examination. The alcohol sniff test (AST), which uses the standard 70% isopropyl alcohol pad, was developed as a quick, reliable measure of olfactory function.

METHODS

Sixty-four patients and 36 healthy control subjects (N = 100) were tested with the AST and with a standard butanol threshold test.

RESULTS

The AST reliably, consistently, and correctly measured olfactory function.

CONCLUSIONS

The AST is a rapid, reliable olfactory test that can be used for screening olfactory function and should be incorporated in the routine cranial nerve examination.

Crystallization and preliminary X-ray analysis of Escherichia coli peptidyl-tRNA hydrolase

Peptidyl-tRNA hydrolase from Escherichia coli, a monomer of 21 kDa, was overexpressed from its cloned gene pth and crystallized by using polyethylene glycol as precipitant. The crystals are orthorhombic and have unit cell parameters a = 47.24 A, b = 63.59 A, and c = 62.57 A. They belong to space group P2(1)2(1)2(1) and diffract to better than 1.2 A resolution. The structure is being solved by multiple isomorphous replacement.

Non-specific helix-induction in charged homopolypeptides by alcohols

The specificity/non-specificity of helix-induction in charged homopolymers such as polylysine and polyglutamic acid, at neutral pH, by various alcohols namely 2,2,2-trifluoroethanol (TFE), methanol, ethanol and 1-propanol is studied. It is found that all the alcohols used, non-specifically induced helical conformation at high concentrations. In addition, the effect(s) of TFE on an all beta-sheet protein, such cardiotoxin analogue I (CTX I) from the Taiwan Cobra (Naja naja atra) is also studied. Evaluation of the helix propensity in the amino-acid sequence of CTX I using helix-coil algorithm, AGADIR, shows a total of 1.15% helical content in the protein. In CTX I, helical conformation is found to be induced at high concentrations of TFE (> or = 70% v/v). Interestingly, upon denaturation and reduction of disulfide bridges in CTX I, helix is found to be induced even at low concentrations of TFE (> or = 20% v/v). The results of this study hints at the possible influence of native tertiary structural interactions and disulfide bridges in the induction of helix by TFE.

Topical vitamin D3 derivatives impair the epidermal permeability barrier in normal mouse skin

BACKGROUND

Calcipotriol, 1,25(OH)2D3 and 1,24(OH)2D3 are potent drugs for the treatment of psoriasis. It has recently been published that these compounds induce epidermal hyperproliferation in hairless mouse skin.

OBJECTIVE

The aim of our study was to examine the effect of vitamin D3 derivatives on epidermal growth, keratinization and permeability barrier function in vivo.

METHODS

Calcipotriol, 1,25(OH)2D3 and 1,24(OH)2D3 in isopropanol or in an ointment formula were applied to normal hairless mouse skin. Transepidermal water loss (TEWL), a marker of cutaneous barrier function, and epidermal proliferation were determined at different time points 0-264 h after treatment. In addition, light and electron microscopy studies were performed.

RESULTS

A single treatment in solution led to a transient (2- to 3-fold) increase in TEWL after application of calcipotriol or 1,25(OH)2D3 and to a 3- to 6-fold increase in epidermal proliferation after application of each of the compounds. Repeated applications also resulted in an up to 3-fold increase in TEWL which persisted for 3 days after the end of the treatment. By light microscopy an increase in epidermal thickness was observed. There was no sign of inflammation. Electron microscopy studies showed the formation of a transitional cell zone as a sign of a premature keratinization.

CONCLUSION

These results demonstrate that in normal mouse skin vitamin D3 and its analogues disrupt the epidermal permeability barrier by induction of epidermal proliferation and premature keratinization but without morphological signs of inflammation.

METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA

Lukins, H. B. (University of Texas, Austin) and J. W. Foster. Methyl ketone metabolism in hydrocarbon-utilizing mycobacteria. J. Bacteriol. 85: 1074-1087. 1963.-Species of Mycobacterium especially M. smegmatis 422, produced the homologous methyl ketones during the oxidation of propane, n-butane, n-pentane, or n-hexane. A carrier-trapping experiment demonstrated the formation of 2-undecanone, as well as 1,11-undecanedioic acid, during the oxidation of undecane-1-C(14). Aliphatic alkane-utilizing mycobacteria were able to grow at the expense of several aliphatic methyl ketones as sole sources of carbon. Other ketones which did not support growth were oxidized by resting bacterial suspensions. M. smegmatis 422 cells grown on propane or acetone were simultaneously adapted to oxidize both substrates, as well as n-propanol. n-Propanol cells were unadapted to propane or acetone. Acetone produced from propane in a medium enriched in D(2)O contained a negligible quantity of D, presumably eliminating propylene as an intermediate in the oxidation. Cells grown at the expense of alkanes or methyl ketones in the presence of O(2) (18) had a higher content of O(18) than did cells grown on terminally oxidized compounds, e.g., primary alcohols or fatty acids. An oxygenase reaction is postulated for the attack on methyl ketones. Acetol was isolated and characterized as an oxidation product of acetone by M. smegmatis 422. Acetol-grown cells had a higher O(18) content than did n-propanol cells, and its utilization appears to involve at least one oxygenase reaction. Acetol produced from acetone in the presence of O(2) (18) was not enriched in the isotope, indicating the occurrence of exchange reactions or of oxygenation reactions at a later stage in the assimilation of acetone and acetol.

Enantioseparation of amino acids and dipeptides using vancomycin as chiral selector in capillary electrophoresis

Vancomycin was applied as chiral selector for the enantiomeric separation of derivatized amino acids and dipeptides. The influence of vancomycin concentration, pH and presence of 2-propanol in the buffer were examined in order to find optimal separation conditions. Optimization was by factorial design. Further, chiral separation of derivatives prepared with three different reagents was compared. These reagents were 9-fluorenylmethyl chloroformate (FMOC), 2-(9-anthryl)ethyl chloroformate (AEOC) and dansyl chloride (dansyl). Optimum resolution was at high vancomycin concentrations, while optimum efficiency was at low vancomycin concentrations. As a consequence of the very high enantioselectivity of vancomycin, the vancomycin concentration below the amount necessary for maximal resolution can be used. Separation efficiency was relatively low, and this could be attributed to adsorption of the selector at the capillary wall. Three factors led to decreased adsorption: application of a pH above the zero mobility pH value, low vancomycin concentrations and the presence of 2-propanol. For amino acids, the resolutions of the different derivatives were: dansyl > AEOC > FMOC, while for dipeptides, the highest selectivity was with AEOC.

THE EFFECTS OF SEVERAL ALCOHOLS ON THE PROPERTIES OF THE SQUID GIANT AXON

The effects of several alcohols on the resting potential, action potential, and voltage-clamp currents of the squid giant axon have been measured. All the alcohols employed are similar in that they depress maximum sodium conductance much more than maximum potassium conductance. Octyl alcohol differs from the others (C₂ through C₅) in that it has less tendency to depolarize the axon. Depolarization is always accompanied by a decrease of g_K near the resting potential, such that the ratio g_K/g_leak is decreased. Steady-state inactivation of the sodium ion current is unaffected by alcohols, as is membrane capacity. Resting membrane conductance is usually decreased by alcohols. The findings are discussed in relation to work on monomolecular films.

Intranasal chemoreception in patients with multiple chemical sensitivities: a double-blind investigation

Multiple chemical sensitivities (MCS) has become an increasingly frequent diagnosis assigned to patients with symptoms associated with exposures to environmental chemicals. Since the characteristic symptoms of MCS are triggered by very low concentrations of chemicals, in the range of olfactory thresholds, it is widely believed that the intranasal chemoreceptive senses are involved in the pathophysiology of MCS. Thus, the present study addressed both the olfactory and trigeminal systems: using a double-blind approach we investigated whether MCS patients show differences in responses after exposure to either room air or low concentrations of a widely used chemical agent (2-propanol). A total of 23 patients participated in the experiments (mean age 47 years; 13 female, 10 male). MCS was diagnosed according to Cullen's criteria Performance of the nasal chemical senses was established by means of chemosensory event-related potentials (CSERP) and subjective measures of olfactory function (odor discrimination, phenylethyl alcohol odor thresholds). CSERP were recorded in response to olfactory (H2S), and trigeminal (CO2) stimuli. The study provided three major results: (1) Approximately 20% of patients diagnosed with MCS presented symptoms regardless of the type of challenge, suggesting the susceptibility of MCS patients to unspecific experimental manipulations. (2) Changes in CSERP latencies indicated a change in the processing of both olfactory and trigeminal stimuli. (3) While odor threshold remained unchanged, the patients' ability to discriminate odors decreased after exposure to room air. In contrast, this decrease was less pronounced after exposure to 2-prop. Summarily, MCS patients respond to challenge with 2-prop with changes of chemosensory perception which might increase their susceptibility to environmentally volatile chemicals. Changes in the pattern of event-related potentials are interpreted as the possible change of the orientation of cortical generators, i.e., neuronal populations that were involved in the processing of chemosensory information. However, investigations in healthy controls are needed in order to draw further conclusions.

[Studies on the evaluation of exposure to industrial chemicals]

Among the biological exposure indices of lead, lead in plasma was the most direct indicator of current exposure. Lead mobilized into plasma as well as in urine could be used as an indicator of the internal dose of lead. The ratio of non-treated to restored activity of delta-aminolevulinic acid dehydratase (ALA-D) was a more specific index than ALA-D activity itself at low levels of lead exposure, excluding the familial or genetic variation in the activity. The methods using HPLC for determining heme intermediate improved the evaluation of the lead effect: delta-aminolevulinic acid in plasma, blood, and urine (ALA-P, ALA-B, and ALA-U), coproporphyrin in urine, and zinc protoporphyrin in blood (ZP). ROC (Receiver operating characteristic) curve analyses indicated that the diagnostic values for lead exposure decreased in the order ALA-D ratio > ALA-D activity = ALA-P > ALA-U = ZP. Pyrimidine 5'-nucleotidase activity or pyrimidine nucleotide concentrations in blood was also useful for the monitoring or diagnosis of lead intoxication. Using the HPLC method with inclusion compounds in the mobile phase, hippuric acid, methylhippuric acids, mandelic acid and phenylglyoxylic acid could be simultaneously determined in the urine of workers exposed to a mixture of toluene, xylenes, and ethylbenzene. The correction of the urinary metabolite concentration for specific gravity or creatinine allowed the more specific evaluation of the solvent exposure. In the biological monitoring of chlorinated hydrocarbons such as trichloroethylene, prolonged excretion of the metabolites resulted in a bias between metabolite concentrations and TWA levels of the solvent in a day. The background levels of 2,5-hexanedione (HD) were affected by acid hydrolysis conditions, age, sex and lipid metabolism. Substances hydrolyzed to HD in urine from non-exposed subjects were different from HD detected in the workers exposed to n-hexane. Urinary concentrations of N-acetyl-S-(N-methylcarbamoyl) cysteine (AMCC) served as an index of the average exposure to N, N-dimethylformamide during several preceding work days and may indicate the internal dose, while N-methylformamide may be an index of daily exposure. A simple and rapid method for the determination of urinary alkoxyacetic acids was recently developed for the biological monitoring of workers exposed to glycolethers and their acetates. Urinary butoxy acetic acid (free plus conjugated ones) could be simply determined by gaschromatography after acid hydrolysis of urine. The urinary acetone or methanol concentration determined by the head space technique was also useful for the biological monitoring of workers exposed to isopropanol and/or acetone, or methanol, respectively. Evaluation of exposure to the solvents described above could be carried out by comparing the urinary metabolite concentrations with reference values and the biological exposure index values which were defined as the urinary metabolite concentration corresponding to the threshold value for each solvent.