The N-terminal signal sequence and the last 98 amino acids are not essential for the secretion of Bacillus sp. TS-23 alpha-amylase in Escherichia coli

A truncated Bacillus sp. TS-23 alpha-amylase gene lacking 96 and 294 bp at its 5' and 3' end respectively was prepared by polymerase chain reaction and cloned into Escherichia coli expression vector, pQE-30, under the control of T5 promoter. SDS-PAGE and activity staining analyses showed that the His6-tagged amylase had a molecular mass of approximately 54 kDa. Isopropyl-beta-d-thiogalactopyranoside (IPTG) induction of E. coli M15 cells bearing the recombinant plasmid resulted in the extracellular production of active amylase. Western blot analysis also revealed that the truncated amylase was present in the periplasmic space and culture medium.

Long-term on-line hemodiafiltration reduces predialysis beta-2-microglobulin levels in chronic hemodialysis patients

BACKGROUND

Hemodiafiltration (HDF) is effective in delaying the surgical need for carpal tunnel syndrome in chronic hemodialysis patients, however, predialysis beta(2)-microglobulin levels were not reduced in most short-term studies. The aim of this study was to assess the effect of long-term and differing frequencies of on-line HDF on serum beta(2)-microglobulin levels in comparison to high-flux hemodialysis (HD).

METHODS

One hundred and twelve patients in the Chang Gung Memorial Hospital Dialysis Unit were divided into three groups to receive different frequencies of on-line HDF alternating with high-flux HD. Group 1 was treated once with HDF and twice with high-flux HD per week (n = 21). Group 2 was treated twice with HDF and once with high-flux HD per week (n = 33). Group 3 was treated with HDF three times per week (n = 58). Analysis was performed to compare the serum beta(2)-microglobulin levels in these groups and to high-flux HD.

RESULTS

After receiving HDF for a mean of 7.9 months, group 3 patients had a reduced predialysis beta(2)-microglobulin level (22.2 +/-5.3 vs. 34.8 +/-6.3 mg/l, p < 0.001), postdialysis beta(2)-microglobulin level (6.3 +/- 2.0 vs. 13.8 +/- 6.8 mg/l, p < 0.001) and an increased beta(2)-microglobulin reduction rate (76.1 +/- 5.6 vs. 61.1 +/- 13.3%, p = 0.03) when compared to high-flux HD. A significant improvement in URR (p = 0.0004), Kt/V (p = 0.0002) and TAC urea levels (p = 0.006) but not nPCR (p = 0.122) was found after patients had been treated with on-line HDF. The beta(2)-microglobulin reduction rate was positively correlated with the overall volume of the replacement solution per session (p < 0.0001). Patients in group 3 had lower predialysis beta(2)-microglobulin levels than those in group 1 and group 2 (22.2 +/- 5.3 vs. 25.2 +/- 7.2 vs. 26.0 +/- 4.2 mg/l, p = 0.02). Furthermore, an inverse correlation was found between the predialysis beta(2)-microglobulin level and the duration of HDF, if patients were treated for more than 12 months (p = 0.031).

CONCLUSION

On-line HDF has an increased dialysis efficiency compared to high-flux dialysis. Long-term HDF further reduced predialysis beta(2)-microglobulin levels, thus, it may provide an improved modality for renal replacement therapy.

Modeling of fugitive dust emission for construction sand and gravel processing plant

Due to rapid economic development in Taiwan, a large quantity of construction sand and gravel is needed to support domestic civil construction projects. However, a construction sand and gravel processing plant is often a major source of air pollution, due to its associated fugitive dust emission. To predict the amount of fugitive dust emitted from this kind of processing plant, a semiempirical model was developed in this study. This model was developed on the basis of the actual dust emission data (i.e., total suspended particulate, TSP) and four on-site operating parameters (i.e., wind speed (u), soil moisture (M), soil silt content (s), and number (N) of trucks) measured at a construction sand and gravel processing plant. On the basis of the on-site measured data and an SAS nonlinear regression program, the expression of this model is E = 0.011.u2.653.M-1.875.s0.060.N0.896, where E is the amount (kg/ton) of dust emitted during the production of each ton of gravel and sand. This model can serve as a facile tool for predicting the fugitive dust emission from a construction sand and gravel processing plant.

Comparison of the metabolic effects of metformin and troglitazone on fructose-induced insulin resistance in male Sprague-Dawley rats

BACKGROUND AND PURPOSE

Insulin resistance is a hallmark of the development of type 2 diabetes. Metformin and troglitazone are oral antidiabetic agents used to reduce insulin resistance. The aim of this study was to compare the metabolic effects of these two drugs in fructose-induced insulin-resistant rodents.

METHODS

Male Sprague-Dawley rats were allocated to receive one of the following four treatments for 6 weeks: normal rat chow (control group, n = 7), high-fructose diet (fructose group, n = 7), high-fructose diet plus metformin (metformin group, n = 8), or high-fructose diet plus troglitazone (troglitazone group, n = 8). Systolic blood pressure (SBP), insulin, free fatty acid (FFA), and triglyceride concentrations were measured as parameters of insulin resistance. Leptin concentration was also measured in the four groups.

RESULTS

The fructose group developed significantly elevated SBP, hyperinsulinemia, and hypertriglyceridemia without significant change in body weight or leptin concentration compared with the control group. The metformin group had significantly reduced body weight (397.9 +/- 40.9 vs 470.1 +/- 59.6 g, p < 0.05), insulin concentration (14.8 +/- 10.5 vs 48.4 +/- 15.2 microU/mL, p < 0.05), triglyceride concentration (75.3 +/- 65.5 vs 250.1 +/- 95.7 mg/dL, p < 0.05), and leptin concentration (3.1 +/- 1.5 vs 6.9 +/- 2.0 ng/mL, p < 0.05) without significant change in SBP (147.8 +/- 5.8 vs 152.4 +/- 13.0 mm Hg, p > 0.05) compared with the fructose group. The troglitazone group had significantly reduced SBP (137.8 +/- 9.2 vs 152.4 +/- 13.0 mm Hg, p < 0.05), insulin concentration (15.0 +/- 13.6 vs 48.4 +/- 15.2 microU/mL, p < 0.05), FFA concentration (38.9 +/- 22.7 vs 78.7 +/- 24.6 mg/dL, p < 0.05), triglyceride concentration (67.6 +/- 32.4 vs 250.1 +/- 95.7 mg/dL, p < 0.05), and leptin concentration (4.4 +/- 2.0 vs 6.9 +/- 2.0 ng/mL, p < 0.05) without significant change in body weight (452.5 +/- 32.8 vs 470.1 +/- 59.6 g, p > 0.05) compared with the fructose group. The metabolic effects of metformin and troglitazone on insulin, FFA, triglyceride, and leptin concentrations were not significantly different. However, metformin treatment resulted in significantly lower body weight (397.9 +/- 40.9 vs 452.5 +/- 32.8 g) and troglitazone treatment in significantly lower SBP (137.8 +/- 9.2 vs 147.8 +/- 5.8 mm Hg) compared to the fructose group, after adjusting for basal values (p < 0.05).

CONCLUSIONS

Both metformin and troglitazone were comparably effective in reducing insulin resistance. Metformin treatment caused body weight reduction but was not effective in reducing SBP. Troglitazone treatment lowered SBP but did not reduce body weight.

Clinical improvement by increased frequency of on-line hemodialfiltration

BACKGROUND/AIMS

In spite of the better efficiency of on-line hemodiafiltration (HDF) compared with conventional hemodialysis (HD), it is relatively expensive. The aim of this study was to assess the advantages in the biochemical, hemodynamic and clinical effects in uremic patients treated with on-line HDF and with different frequencies of combination high-flux HD.

METHODS

One hundred eleven patients were divided into four groups receiving different frequencies of on-line HDF (thrice, twice, once per week) and high-flux HD.

RESULTS

Hemodynamic parameters including maximum drop of systolic blood pressure, episodes of symptomatic hypotension and mean saline infusion volumes during dialysis were reduced when frequencies of on-line HDF were increased. Significant improvements in urea kinetic were observed when frequencies of on-line HDF were increased. On-line HDF significantly reduced the amount of erythropoietin needed and improved intra- and inter-dialysis symptoms, physical well-being, menstruation and skin pigmentation when frequency of HDF is increased to three time per week.

CONCLUSION

On-line HDF offers a better cardiovascular stability and clinical improvement. Thrice weekly on-line HDF offers a significant benefit when compared with lower frequencies of HDF per week and high-flux HD.

Thyrotoxic periodic paralysis in a patient abusing thyroxine for weight reduction

Thyrotoxic periodic paralysis is a rare endocrine disorder most prevalent among individuals of Asian descent that presents as proximal muscle weakness, hypokalemia, and signs of hyperthyroidism. We present an unusual patient with previous normal thyroid function who had abused thyroxine as antiobesity pills and developed periodic paralysis affecting the upper and lower limbs.

Steroid-sensitive anemia in a boy on dialysis--an association with Kimura disease

The cause of hypereosinophilia (EO) in hemodialysis (HD) patients is multifactorial and is felt to be a benign laboratory abnormality related to dialysis or uremia. Kimura disease (KD) is an angiolymphoid proliferative disorder of unknown etiology. Many cases are associated with nephrotic syndrome in children; however, it has seldom been reported in children on dialysis. We report here a 13-year-old boy who developed persistent EO and subsequent anemia after maintenance HD; he later developed KD. The atypical clinical manifestation of KD and its relationship to HD and erythropoietin hyposensitive anemia in this patient are discussed.

Peripheral venopuncture as temporary vascular access in rhabdomyolysis-induced acute renal failure related to frog leaps: case report

Rhabdomyolysis, or acute muscle destruction, may be accompanied by myoglobinemia, myoglobinuria, and an elevated serum creatine kinase level. The disorder has many potential causes, the most common one in otherwise healthy people being severe exercise. Rhabdomyolysis has many complications, but the most important one is acute renal failure. We describe a man with rhabdomyolysis-induced acute renal failure occurring after frog leaps. During 3 dialytic sessions, we practiced direct puncture of peripheral veins of the antecubital fossa as temporary vascular access for this patient. His renal function improved, after which he was discharged with a smooth clinical course.

Potent fibrinolytic enzyme from a mutant of Bacillus subtilis IMR-NK1

A mutant of Bacillus subtilis IMR-NK1, which is used for the production of domestic "natto" in Taiwan, produced high fibrinolytic enzyme activity by solid-state fermentation using wheat bran as medium. In addition, a strong fibrinolytic enzyme was purified from the cultivation media. The purified enzyme was almost homogeneous, as examined by SDS-PAGE and capillary electrophoresis. The enzyme had an optimal pH of 7.8, an optimal temperature of 55 degrees C, and a K(m) of 0.15% for fibrin hydrolysis. The molecular mass estimated by gel filtration was 31.5 kDa, and the isoelectric point estimated by isoelectric focusing electrophoresis was 8.3. The enzyme also showed activity for hydrolysis of fibrinogen, casein, and several synthetic substrates. Among the synthetic substrates, the most sensitive substrate was N-succinyl-Ala-Ala-Pro-Phe-pNA. PMSF and NBS almost completely inhibited the activity of the enzyme. These results indicate that the enzyme is a subtilisin-like serine protease, similar to nattokinase from Bacillus natto.

Nalmefene to prevent epidural narcotic side effects in pediatric patients: a pharmacokinetic and safety study

STUDY OBJECTIVE

To determine the pharmacokinetics and preliminary efficacy of nalmefene in children in preventing epidural-induced narcotic side effects.

DESIGN

Double-blind, placebo-controlled study.

SETTING

University-affiliated children's hospital.

PATIENTS

Thirty-four children (aged 2-12 yrs) undergoing cardiothoracic surgery with epidural anesthesia.

INTERVENTIONS

Patients were randomized to receive intravenous bolus nalmefene 1 microg/kg or placebo.

MEASUREMENTS AND MAIN RESULTS

Six blood samples (one before nalmefene administration and five from 13 randomly designated time points) from each patient were assayed to determine plasma nalmefene concentrations. Patients were assessed for pain, nausea, vomiting, and urinary retention for 24 hours after administration. Concentration-time data were analyzed by a limited sampling strategy with adult pharmacokinetic parameters used as Bayesian priors. A two-compartment, first-order model was fitted to the data using ADAPT II. Pharmacokinetic parameter estimates in these patients were similar to values reported in adults. The initial disposition half-life (t(1/2alpha)) was 0.36+/-0.11 hour, the terminal elimination half-life (t(1/2beta)) 8.7+/-2.3 hours, clearance 0.729+/-0.172 L/kg/hr, and steady-state volume of distribution 7.21+/-2.49 L/kg. Ability to prevent epidural narcotic-induced side effects could not be documented at the 1-microg/kg dose. No statistically significant differences were noted between study and placebo groups with regard to pain, nausea, vomiting, or urinary retention.

CONCLUSION

Nalmefene has similar pharmacokinetics in children as in adults. It was administered safely to these patients and did not produce unmanageable pain.

Direct peripheral venopuncture: another new choice of temporary vascular access

BACKGROUND

Femoral, subclavian, and internal jugular veins access have been widely used for temporary vascular access for hemodialysis, but their use has been associated with a significant complication rate. We report in three selected hemodialysis patients with the procedure of direct peripheral venopuncture as temporary vascular access to reduce complications.

METHODS

We have demonstrated hemodialysis via direct puncture of peripheral veins of the antecubital fossa (cephalic vein in the process of arterial inflow to dialyzer and venous outflow from dialyzer to basilic vein) as temporary vascular access for these patients.

RESULTS

Renal function of case 1 and case 2 progress to normal status after several sessions of dialytic therapy as well as quit hemodialysis, and case 3 successfully shifts to peritoneal dialysis following four sessions of dialytic therapy.

CONCLUSIONS

We recommend this short-term access contribute a important additional new choice in selected patients with acute, reversible renal failure, obstructive uropathy, initiation of peritoneal dialysis, patients on peritoneal dialysis with peritonitis, or under plasmapheresis therapy.

Cyclosporine bioavailability of Neoral and Sandimmune in white and black de novo renal transplant recipients. Neoral Study Group

Black renal transplant recipients have inferior graft outcomes when compared to whites. The relative bioavailability of cyclosporine (CsA) with the Sandimmune (SIM) formulation is lower in black recipients when compared to whites. To study relative CsA bioavailability in the Neoral formulation, 18 black and 78 white de novo renal transplant recipients were randomized in a multicenter, double-blind, parallel group study to receive either SIM or Neoral capsules twice a day for 12 weeks. After an overnight fast, CsA whole blood levels (TDx) were collected during 12 hours after the morning dose and 12 hours after the evening dose with a standardized meal. Pharmacokinetic profiles were obtained at the end of weeks 1, 4, 8, and 12. Initial CsA dose was 5 mg/kg twice a day; subsequent doses were titrated to target trough CsA levels. Area under the blood concentration vs. time curve (AUC), peak blood concentration (Cmax) and time to Cmax(Tmax) were obtained from 16 black and 73 white patients. Food conditions (fed and fasting) were averaged, and data was dose-normalized. For black recipients, Neoral was significantly more bioavailable than SIM only during week 1; there was also a consistent trend to higher cyclosporine bioavailability at weeks 4, 8, and 12. For whites, there were significant differences in favor of Neoral at all time periods. No significant differences in relative bioavailability were noted between races for either SIM or Neoral except for a higher Cmax in white patients given Neoral. Neoral is better absorbed than SIM in both blacks and whites. These data suggest that Neoral is the superior CsA preparation for all racial groups.

Small functional adrenal cortical adenoma: treatment with CT-guided percutaneous acetic acid injection--report of three cases

Two patients with Conn syndrome and one patient with Cushing syndrome underwent computed tomography (CT)-guided tumor ablation with a total of 5-11 mL of 50% acetic acid injected into their adrenal nodule (1.3-3.3 cm in diameter). No major complications were encountered during or after the procedure. All patients were symptom free with normal laboratory test results for at least 1-year follow-up. CT images showed complete cystic change with tumor size regression. Our preliminary results suggest that percutaneous acetic acid injection is a safe and effective alternative for treatment of small functional adrenal cortical adenoma.

Novel protein kinase C inhibitors: synthesis and PKC inhibition of beta-substituted polythiophene derivatives

A series of beta-substituted polythiophene derivatives was synthesized through palladium-catalyzed coupling reaction. Their structure-protein kinase C (PKC) inhibitory activity relationship was studied. The carboxaldehyde and hydroxymethyl derivatives of alpha-terthiophene were potent PKC inhibitors (IC50 = 10(-7) M).

Safety of withdrawing inhaled nitric oxide therapy in persistent pulmonary hypertension of the newborn

OBJECTIVE

Because of case reports describing hypoxemia on withdrawal of inhaled nitric oxide (I-NO), we prospectively examined this safety issue in newborns with persistent pulmonary hypertension who were classified as treatment successes or failures during a course of I-NO therapy.

METHODS

Randomized, placebo-controlled, double-masked, dose-response clinical trial at 25 tertiary centers from April 1994 to June 1996. Change in oxygenation and outcome (death and/or extracorporeal membrane oxygenation) during or immediately after withdrawing I-NO were the principal endpoints. Patients (n = 155) were term infants, <3 days old at study entry with echocardiographic evidence of persistent pulmonary hypertension of the newborn. Exclusion criteria included previous surfactant treatment, high-frequency ventilation, or lung hypoplasia. Withdrawal from treatment gas (0, 5, 20, or 80 ppm) started once treatment success or failure criteria were met. Withdrawal of treatment gas occurred at 20% decrements at <4 hours between steps.

RESULTS

The patient profile was similar for placebo and I-NO groups. Treatment started at an oxygenation index (OI) of 25 +/- 10 (mean +/- SD) at 26 +/- 18 hours after birth. For infants classified as treatment successes (mean duration of therapy = 88 hours, OI <10), decreases in the arterial partial pressure of oxygen (PaO(2)) were observed only at the final step of withdrawal. On cessation from 1, 4, and 16 ppm, patients receiving I-NO demonstrated a dose-related reduction in PaO(2) (-11 +/- 23, -28 +/- 24, and -50 +/- 48 mm Hg, respectively). For infants classified as treatment failures (mean duration of therapy = 10 hours), no change in OI occurred for the placebo group (-13 +/- 36%, OI of 31 +/- 11 after the withdrawal process); however a 42 +/- 101% increase in OI to 46 +/- 21 occurred for the pooled nitric oxide doses. One death was possibly related to withdrawal of I-NO.

CONCLUSION

For infants classified as treatment successes, a dose response between the I-NO dose and decrease in PaO(2) after discontinuing I-NO was found. A reduction in I-NO to 1 ppm before discontinuation of the drug seems to minimize the decrease in PaO(2) seen. For infants failing treatment, discontinuation of I-NO could pose a life-threatening reduction in oxygenation should extracorporeal membrane oxygenation not be readily available or I-NO cannot be continued on transport.

Improved cyclosporine bioavailability in black pediatric liver transplant recipients after administration of the microemulsion formulation

Black transplant recipients are associated with low cyclosporine bioavailability, which may contribute to the poorer clinical outcomes observed with these patients. In this analysis, we compared cyclosporine exposure in black (n = 9) and nonblack (n = 18) pediatric maintenance liver transplant recipients by using steady-state pharmacokinetic profiles obtained after administration of the original and microemulsion formulations of cyclosporine. Treatment with the original cyclosporine formulation resulted in lower mean dose-normalized, area under the concentration-versus-time curve values for black compared with nonblack pediatric liver transplant recipients. On conversion to the microemulsion formulation of cyclosporine, black and nonblack patients experienced increases in cyclosporine bioavailability of 102% and 39%, respectively (P =.009 and P =.001). Because the increase in mean bioavailability was substantially greater for blacks, area under the concentration-versus-time curve values for this pediatric subpopulation became similar to those levels obtained for nonblacks receiving the microemulsion formulation for cyclosporine. When patients were further stratified by age, ethnic differences in bioavailability with the original formulation of cyclosporine were most apparent in the 1- to 5-year age group. Conversion to the microemulsion formulation resulted in a 164% increase (P =.05) in bioavailability for black patients within this age group such that, again, these levels became similar to area under the concentration-versus-time curve values obtained for young nonblacks receiving cyclosporine for microemulsion. Improvements in cyclosporine bioavailability after administration of the microemulsion formulation of cyclosporine may translate to improved long-term graft and patient outcomes for black pediatric liver transplant recipients.

Evidence for increased functional vascular Na+/K+ pump activity in the obese Zucker rat

Insulin is known to stimulate Na+/K+ ATPase and to relax vascular smooth muscle. We hypothesized that vascular tone in the obese Zucker (fa/fa) rat, a hyperinsulinemic model in which hypertension can develop, may be influenced by insulin's ability to stimulate Na+/K+ ATPase at the vascular level. We studied isometric preparations of tail and femoral arteries from 10-wk-old, male obese Zucker rats, which were hyperinsulinemic but still normotensive vs. lean controls. Sensitivity to potassium-induced relaxations, an index of vascular Na+/K+ ATPase activity was significantly greater in the obese Zucker rat than control. Sensitivity to transmural-nerve-stimulation-induced contractions was decreased in the femoral and tail arteries from obese rats as compared with lean controls. Insulin (50 to 200 mU/ml) mimicked potassium-induced relaxations in the femoral artery, an effect that was significantly greater in the obese group. These data suggest that in the young hyperinsulinemic Zucker rat, insulin has a stimulatory effect on the vascular Na+/K+ pump, which may be associated with a decreased presynaptic adrenergic influence on vascular tone. Development of resistance to these vascular relaxant effects of insulin with advancing age might contribute to the onset of hypertension in this model.

Is the short insulin tolerance test safe and reproducible?

The short insulin tolerance test (SITT) is described as a simple method to measure insulin sensitivity. To investigate the safety and reproducibility of the SITT, 16 healthy volunteers underwent two SITTs within 1 week. Intravenous insulin (0.05 U kg(-1) body weight) was injected into an antecubital vein. Blood samples were collected from the contralateral antecubital vein. The insulin-induced glucose disposal rate (Kitt) was calculated from the slope of the regression line of the logarithm of blood glucose against time during the first 3-15 min. Plasma glucose concentrations fell below 2.8 mmol l(-1) in 4 of the 32 tests and below 2.2 mmol I(-1) in 1 of these 4. Five subjects had mild hypoglycaemic symptoms, three of whom had plasma glucose concentrations below 2.8 mmol l(-1) in at least one SITT. The mean Kitt was 4.2% min(-1) (range 0.8-8.4) for the first test and 3.4% min(-1) (range 0.1-6.8) for the second test. The mean within-subject coefficient of variation was 30.7%. We conclude that SITT should be applied with caution especially on insulin sensitive subjects and has poor reproducibility using 0.05 U kg(-1) body weight of insulin injection, venous sampling, uncontrolled physical activity and uncontrolled dietary composition. Whether 0.1 U kg(-1) body weight of insulin injection and arterialized venous blood sampling as in the original description of this test can improve the reproducibility of the SITT needs further investigation.

Novel protein kinase C inhibitors: alpha-terthiophene derivatives

A series of alpha-terthiophene derivatives were prepared and their protein kinase C inhibitory activity were evaluated. The aldehyde derivatives were most potent inhibitors (IC50 < 1 microM). alpha-Terthiophene monoaldehyde was inactive in the inhibitions of protein kinase A, mitogen activated protein kinase and protein tyrosine kinase.

Optimal selection procedures for abbreviated area under the curve (AAUC) of blood concentration versus time for drug blood concentration levels

It has become common to collect blood samples from patients for phase II/III clinical trials to investigate pharmacokinetic/pharmacodynamic relationships. However, the frequency of blood samples drawn from patients is limited due to clinical or pharmacoeconomic reasons. We discuss some sampling schemes for an immunosuppressive drug in phase III studies. Selection criteria and statistical approaches are discussed to select blood-sampling time points in four scenarios from a single study and from combined multiple studies: (1) Area under the curve (AUC) only without constraint, (2) AUC and Cmax simultaneously without constraint, (3) AUC only with constraint(s), and (4) AUC and Cmax simultaneously with constraint(s).

Purification and properties of beta-N-Acetylhexosaminidase from cabbage

beta-N-Acetylhexosaminidase was purified from the extract of cabbage by sequential steps of ammonium sulfate fractionation, chromatofocusing, DEAE-Sepharose CL-6B ion exchange chromatography and Sephacryl S-200 HR gel filtration. By these steps, the purity of the enzyme increased by 256 fold with a recovery of 8%. The purified enzyme was homogeneous as examined by native PAGE. It showed an optimal pH of 4, an optimal temperature of 60 degrees C and a Km of 0.94 mM for hydrolysis of pNp-beta-GlcNAc. The molecular mass of the enzyme determined from filtration through Sephacryl S-200 was 150 kDa. Three subunits with molecular mass of 64, 57 and 51 kDa were observed as determined by SDS-PAGE. NBS (0.025 mM), DEPC (3 mM) and WRK (30 mM) significantly inhibited the activity of the enzyme. The enzyme also showed activity toward pNp-beta-GalNAc, N,N'-diacetylchitobiose, N,N',N"-triacetylchitotriose and N,N',N",N"'-tetraacetyl chitotetraose but showed no activity toward pNp-alpha-GlcNAc, chitin and ethylene glycol chitin.

NMR characterization of hydrocarbon gas in porous media

Laboratory investigations of nuclear magnetic resonance (NMR) relaxation properties of methane gas in bulk and in porous media are reported. Measurements were performed for methane alone and together with water in glass bead packs and Bentheimer sandstone. Results indicate that surface relaxation effects can be significant and that diffusion effects dominate observed T2 relaxation.

The effect of wait time on T2 distributions from NMR experiments

Nuclear magnetic resonance (NMR) relaxation curves for both T1 and T2 on two brine-saturated core plugs have been measured at 1 MHz. T2 distributions were extracted from Carr-Purcell-Meiboom-Gill (CPMG) measurements using different wait times between consecutive echo sequences. The analysis was performed with both a limited number of exponentials and a continuous B-spline basis. The distributions depend strongly on wait time. The distributions were generally restored to the true distributions when a wait time correction was applied.