Direct detection of circular polarized light in helical 1D perovskite-based photodiode.

Detection of circularly polarized light (CPL) has a high potential for development of various optical technologies. Conventional photodetectors require optical polarizers on the device to detect polarized light, and this causes substantial losses of sensitivity and resolution in light detection. Here, we report direct CPL detection by a photodiode using a helical one-dimensional (1D) structure of lead halide perovskites composed of naphthylethylamine-based chiral organic cations. The 1D structure with face-sharing (PbI6)4- octahedral chains whose helicity is largely affected by chiral cations shows intense circular dichroism (CD) signals over 3000 mdeg at 395 nm with the highly anisotropy factor (g CD) of 0.04. This high CD enables photocurrent detection with effective discrimination between left-handed and right-handed CPLs. The CPL detector based on this 1D perovskite achieved the highest polarization discrimination ratio of 25.4, which largely surpasses the direct detecting CPL devices (<4) using chiral plasmonic metamaterials and organic materials.

Imaging Differences between Neuromyelitis Optica Spectrum Disorders and Multiple Sclerosis: A Multi-Institutional Study in Japan.

BACKGROUND AND PURPOSE: Both clinical and imaging criteria must be met to diagnose neuromyelitis optica spectrum disorders and multiple sclerosis. However, neuromyelitis optica spectrum disorders are often misdiagnosed as MS because of an overlap in MR imaging features. The purpose of this study was to confirm imaging differences between neuromyelitis optica spectrum disorders and MS with visually detailed quantitative analyses of large-sample data. MATERIALS AND METHODS: We retrospectively examined 89 consecutive patients with neuromyelitis optica spectrum disorders (median age, 51 years; range, 16-85 years; females, 77; aquaporin 4 immunoglobulin G-positive, 93%) and 89 with MS (median age, 36 years; range, 18-67 years; females, 68; relapsing-remitting MS, 89%; primary-progressive MS, 7%; secondary-progressive MS, 2%) from 9 institutions across Japan (April 2008 to December 2012). Two neuroradiologists visually evaluated the number, location, and size of all lesions using the Mann-Whitney U test or the Fisher exact test. RESULTS: We enrolled 79 patients with neuromyelitis optica spectrum disorders and 87 with MS for brain analysis, 57 with neuromyelitis optica spectrum disorders and 55 with MS for spinal cord analysis, and 42 with neuromyelitis optica spectrum disorders and 14 with MS for optic nerve analysis. We identified 911 brain lesions in neuromyelitis optica spectrum disorders, 1659 brain lesions in MS, 86 spinal cord lesions in neuromyelitis optica spectrum disorders, and 102 spinal cord lesions in MS. The frequencies of periventricular white matter and deep white matter lesions were 17% and 68% in neuromyelitis optica spectrum disorders versus 41% and 42% in MS, respectively (location of brain lesions, P < .001). We found a significant difference in the distribution of spinal cord lesions between these 2 diseases (P = .024): More thoracic lesions than cervical lesions were present in neuromyelitis optica spectrum disorders (cervical versus thoracic, 29% versus 71%), whereas they were equally distributed in MS (46% versus 54%). Furthermore, thoracic lesions were significantly longer than cervical lesions in neuromyelitis optica spectrum disorders (P = .001), but not in MS (P = .80). CONCLUSIONS: Visually detailed quantitative analyses confirmed imaging differences, especially in brain and spinal cord lesions, between neuromyelitis optica spectrum disorders and MS. These observations may have clinical implications.

Sex-based differences in CD103+ dendritic cells promote female-predominant Th2 cytokine production during allergic asthma.

BACKGROUND: Gender disparities in adult patients with asthma regarding its prevalence and severity are mainly due to enhanced type 2 T-helper (Th2) cytokine production in female patients compared to that in male patients. However, the pathways mediating this effect remain unclear. OBJECTIVE: We aimed to determine the roles of two major subsets of dendritic cells (DCs) in females, specifically those displaying CD11b or CD103, during enhanced Th2 priming after allergen exposure, using an ovalbumin-induced asthma mouse model. METHODS: Sex-based differences in the number of DCs at inflamed sites, costimulatory molecule expression on DCs, and the ability of DCs to differentiate naïve CD4+ T cells into Th2 population were evaluated after allergen exposure in asthmatic mice. In addition, we assessed the role of 17ß-oestradiol in CD103+ DC function during Th2 priming in vitro. RESULTS: The number of CD11bhigh DCs and CD103+ DCs in the lung and bronchial lymph node (BLN) was increased to a greater extent in female mice than in male mice at 16 to 20 hours after ovalbumin (OVA) inhalation. In BLNs, CD86 and I-A/I-E expression levels and antigen uptake ability in CD103+ DCs, but not in CD11bhigh DCs, were greater in female mice than in male mice. Furthermore, CD4+ T cells cultured with CD103+ DCs from female mice produced higher levels of interleukin (IL)-4, IL-5, and IL-13, compared with CD4+ T cells cultured with CD103+ DCs from male mice. The 17ß-oestradiol-oriented enhancement of CD86 expression on CD103+ DCs after allergen exposure induced the enhanced IL-5 production from CD4+ T cells. CONCLUSIONS AND CLINICAL RELEVANCE: These findings suggest that with regard to asthma, enhanced Th2 cytokine production in females might be attributed to 17ß-oestradiol-mediated Th2-oriented CD103+ DCs in the BLN.

Formamidine and cesium-based quasi-two-dimensional perovskites as photovoltaic absorbers.

Formamidine (FA) and cesium (Cs) cations were introduced into quasi-two-dimensional (2D) perovskites as B site cations. The unique crystalline growth of the resulting (n-C6H13NH3)2FAPb2I7, which promotes charge transport in photovoltaic solar cells, was confirmed, as was the stability of this material. The photovoltaic properties of (n-C6H13NH3)2FAPb2I7 were found to be superior to those of other homologous quasi-2D perovskite compounds.

Adenosquamous carcinoma of the oesophagus in a dog.

A six-year-old mixed-breed male dog weighing 7.0 kg was presented with chronic vomiting and regurgitation. Endoscopic examination revealed prominent oesophageal dilation in the thoracic region, multiple small greyish-white nodules over the oesophageal lumen and cauliflower-like masses in the caudal oesophagus. Histopathological studies revealed a characteristic pattern of coexisting elements of infiltrating adenocarcinoma and squamous cell carcinoma. Immunohistochemical staining with anti-cytokeratin AE1 + AE3 was positive in both types of neoplastic cells. Neoplastic glandular cells stained positively for cytokeratin 8 while neoplastic squamous cells stained positively for cytokeratin 5/6. On the basis of these findings, the dog was diagnosed with oesophageal adenosquamous carcinoma. The case history and findings suggest that the malignancy might have developed from Barrett's oesophagus following irritation of the oesophageal mucosa due to chronic vomiting and regurgitation.

Assessment of biodiversity in Chilean cattle using the distribution of major histocompatibility complex class II BoLA-DRB3 allele.

Bovine leukocyte antigens (BoLAs) are used extensively as markers for bovine disease and immunological traits. In this study, we estimated BoLA-DRB3 allele frequencies using 888 cattle from 10 groups, including seven cattle breeds and three crossbreeds: 99 Red Angus, 100 Black Angus, 81 Chilean Wagyu, 49 Hereford, 95 Hereford × Angus, 71 Hereford × Jersey, 20 Hereford × Overo Colorado, 113 Holstein, 136 Overo Colorado, and 124 Overo Negro cattle. Forty-six BoLA-DRB3 alleles were identified, and each group had between 12 and 29 different BoLA-DRB3 alleles. Overo Negro had the highest number of alleles (29); this breed is considered in Chile to be an 'Old type' European Holstein Friesian descendant. By contrast, we detected 21 alleles in Holstein cattle, which are considered to be a 'Present type' Holstein Friesian cattle. Chilean cattle groups and four Japanese breeds were compared by neighbor-joining trees and a principal component analysis (PCA). The phylogenetic tree showed that Red Angus and Black Angus cattle were in the same clade, crossbreeds were closely related to their parent breeds, and Holstein cattle from Chile were closely related to Holstein cattle in Japan. Overall, the tree provided a thorough description of breed history. It also showed that the Overo Negro breed was closely related to the Holstein breed, consistent with historical data indicating that Overo Negro is an 'Old type' Holstein Friesian cattle. This allelic information will be important for investigating the relationship between major histocompatibility complex (MHC) and disease.

Distribution and characteristics of bovine leukemia virus integration sites in the host genome at three different clinical stages of infection.

Bovine leukemia virus (BLV) is an oncogenic retrovirus closely related to human T-cell lymphotropic virus. BLV-infected cattle are categorized as asymptomatic carriers or as having persistent lymphocytosis or enzootic bovine leukemia, depending on the clinical stage. We investigated the BLV integration site distribution at three BLV clinical stages and examined genome sequence features around the integration sites. In all, 264 BLV integration sites, at various locations on each chromosome, were identified in 28 cattle by inverse PCR and BLAST searches. Approximately one-third of BLV proviruses were independently integrated within transcriptional units, and approximately 10 % were integrated near transcription start sites. Moreover, less than 7 % of BLV integration sites were located near CpG islands. BLV did not preferentially integrate into transcriptionally active regions during any of the clinical stages. At the nucleotide level, regions around BLV integration points were significantly A/T rich with weak sequence consensus. BLV preferentially integrated within long interspersed nuclear repeat elements. Although BLV integration sites may not be associated with disease progression, integration is selective at the nucleotide level.

Time course of axial and radial diffusion kurtosis of white matter infarctions: period of pseudonormalization.

BACKGROUND AND PURPOSE: Diffusion kurtosis is a statistical measure for quantifying the deviation of the water diffusion profile from a Gaussian distribution. The current study evaluated the time course of diffusion kurtosis in patients with cerebral infarctions, including perforator, white matter, cortical, and watershed infarctions. MATERIALS AND METHODS: Subjects were 31 patients, representing 52 observations of lesions. The duration between the onset and imaging ranged from 3 hours to 122 days. Lesions were categorized into 4 groups listed above. Diffusion kurtosis images were acquired with b-values of 0, 1000, and 2000 s/mm(2) applied in 30 directions; variables including DWI signal, ADC, fractional anisotropy, radial diffusivity, axial diffusivity, radial kurtosis, and axial kurtosis, were obtained. The time courses of the relative values (lesion versus contralateral) for these variables were evaluated, and the pseudonormalization period was calculated. RESULTS: Diffusion kurtosis was highest immediately after the onset of infarction. Trend curves showed that kurtosis decreased with time after onset. Pseudonormalization for radial/axial kurtosis occurred at 13.2/59.9 days for perforator infarctions, 33.1/40.6 days for white matter infarctions, 34.8/35.9 days for cortical infarctions, and 34.1/28.2 days after watershed infarctions. For perforator infarctions, pseudonormalization occurred in the following order: radial kurtosis, ADC, axial kurtosis, and DWI. CONCLUSIONS: Diffusion kurtosis variables in lesions increased early after infarction and decreased with time. Information provided by diffusion kurtosis imaging, including axial and radial kurtosis, seems helpful in conducting a detailed evaluation of the age of infarction, in combination with T2WI, DWI, and ADC.

The great diversity of major histocompatibility complex class II genes in Philippine native cattle.

Bovine leukocyte antigens (BoLA) are extensively used as markers for bovine disease and immunological traits. However, none of the BoLA genes in Southeast Asian breeds have been characterized by polymerase chain reaction (PCR)-sequence-based typing (SBT). Therefore, we sequenced exon 2 of the BoLA class II DRB3 gene from 1120 individual cows belonging to the Holstein, Sahiwal, Simbrah, Jersey, Brahman, and Philippine native breeds using PCR-SBT. Several cross-breeds were also examined. BoLA-DRB3 PCR-SBT identified 78 previously reported alleles and five novel alleles. The number of BoLA-DRB3 alleles identified in each breed from the Philippines was higher (71 in Philippine native cattle, 58 in Brahman, 46 in Holstein × Sahiwal, and 57 in Philippine native × Brahman) than that identified in breeds from other countries (e.g., 23 alleles in Japanese Black and 35 in Bolivian Yacumeño cattle). A phylogenetic tree based on the DA distance calculated from the BoLA-DRB3 allele frequency showed that Philippine native cattle from different Philippine islands are closely related, and all of them are closely similar to Philippine Brahman cattle but not to native Japanese and Latin American breeds. Furthermore, the BoLA-DRB3 allele frequency in Philippine native cattle from Luzon Island, located in the Northern Philippines was different from that in cattle from Iloilo, Bohol, and Leyte Islands, which are located in the Southern Philippines. Therefore, we conclude that Philippine native cattle can be divided into two populations, North and South areas. Moreover, a neutrality test revealed that Philippine native cattle from Leyte showed significantly greater genetic diversity, which may be maintained by balancing selection. This study shows that Asian breeds have high levels of BoLA-DRB3 polymorphism. This finding, especially the identification of five novel BoLA-DRB3 alleles, will be helpful for future SBT studies of BoLA-DRB3 alleles in East Asian cattle.

Identification of bovine leukocyte antigen class II haplotypes associated with variations in bovine leukemia virus proviral load in Japanese Black cattle.

Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis, which is the most common neoplastic disease of cattle. Bovine leukocyte antigen (BoLA) is strongly involved in the subclinical progression of BLV infections. Recent studies show that the BoLA-DRB3 gene might play a direct role in controlling the number of BLV-infected peripheral B lymphocytes in vivo in Holstein cattle. However, the specific BoLA class II allele and DRB3-DQA1 haplotypes determining the BLV proviral load in Japanese Black cattle are yet to be identified. In this study, we focused on the association of BLV proviral load and polymorphism of BoLA class II in Japanese Black cattle. We genotyped 186 BLV-infected, clinically normal cattle for BoLA-DRB3 and BoLA-DQA1 using a polymerase chain reaction-sequence-based typing method. BoLA-DRB3*0902 and BoLA-DRB3*1101 were associated with a low proviral load (LPVL), and BoLA-DRB3*1601 was associated with a high proviral load (HPVL). Furthermore, BoLA-DQA1*0204 and BoLA-DQA1*10012 were related to LPVL and HPVL, respectively. Furthermore, we confirmed the correlation between the DRB3-DQA1 haplotype and BLV proviral load. Two haplotypes, namely 0902B or C (DRB3*0902-DQA1*0204) and 1101A (DRB3*1101-DQA1*10011), were associated with a low BLV proviral load, whereas one haplotype 1601B (DRB3*1601-DQA1*10012) was associated with a high BLV proviral load. We conclude that resistance is a dominant trait and susceptibility is a recessive trait. Additionally, resistant alleles were common between Japanese Black and Holstein cattle, and susceptible alleles differed. This is the first report to identify an association between the DRB3-DQA1 haplotype and variations in BLV proviral load.

Identification and diversity of bovine major histocompatibility complex class II haplotypes in Japanese Black and Holstein cattle in Japan.

Bovine leukocyte antigen (BoLA), the major histocompatibility complex of cattle, is one of the most polymorphic gene clusters. We genotyped a population of 109 Japanese Black and 39 Holstein cattle to analyze their BoLA class II haplotypes, BoLA-DRB3 locus, 5 BoLA-DQA loci, and 5 BoLA-DQB loci. We identified 26 previously reported DRB3 alleles, 22 previously reported and 3 new DQA alleles, and 24 previously reported and 6 new DQB alleles. A dendrogram was constructed based on the predicted amino acid sequences of the α1 or ß1 domains encoded by BoLA-DQA or -DQB alleles, which revealed that DQA alleles were clustered into 5 loci, whereas DQB alleles could not be clearly assigned to specific DQB loci. The BoLA-DRB3-DQA-DQB haplotypes were sorted by sequential analytical processes, and 42 distinct haplotypes, including 11 previously published haplotypes and 31 novel haplotypes, were defined. Strong linkage disequilibrium was present in the BoLA genes. We also compared DRB3-DQA1 haplotype frequencies between 507 Japanese Black and 143 Holstein cattle. Thirty-nine DRB3-DQA1 haplotypes were identified, including 29 haplotypes from Japanese Black and 22 haplotypes from Holstein cattle. The majority of the haplotypes could be identified in both breeds, although several haplotypes were identified in only a single breed. This is the first report presenting a detailed study of the BoLA class II haplotype in Japanese Black and Holstein cattle in Japan.

A new method for typing bovine major histocompatibility complex class II DRB3 alleles by combining two established PCR sequence-based techniques.

Recently, two polymerase chain reaction sequence-based typing (PCR-SBT) methods were reported for the genotyping of the bovine leukocyte antigen (BoLA)-DRB3. One technique is a single PCR-SBT (sPCR-SBT) method that generates heterozygous sequences that are subsequently analyzed by the haplofinder program, while the other technique is a nested PCR-SBT (nPCR-SBT) method that allows the analysis of heterozygous sequences using the assign 400ATF software. In this study, these techniques were compared and then integrated to produce an improved genotyping method. The primer set used for sPCR-SBT was more accurate than those used for nPCR-SBT. Combining sPCR-SBT with the assign 400ATF software previously reported for nPCR-SBT enables rapid and accurate genotyping of a large number of DNA samples.

Transient hyperintensity in the subthalamic nucleus and globus pallidus of newborns on T1-weighted images.

BACKGROUND AND PURPOSE: In the brains of newborns, changes in signal intensity in most structures can be explained by the development of myelination. However, there are some structures for which signal intensity changes cannot be accounted for by myelination alone. We examined the STN and globus pallidus signal intensities and tried to determine whether a relationship exists between the signal intensity and the postnatal age or the gestational age at the examination. MATERIALS AND METHODS: We examined T1WI and T2WI obtained from 79 neonates who showed normal development at their 2-year follow-up examinations. We performed both qualitative and quantitative (signal intensity ratio to the thalamus) evaluation of the STN and globus pallidus signals, and we examined the correlation between signal intensity changes and the age of neonates. RESULTS: With increasing postnatal age at examination, the high signal intensity on the T1WI for both STN and globus pallidus diminished. Although the disappearance of this hyperintensity was well correlated with the postnatal age at examination for both the qualitative and quantitative studies, there was no correlation with gestational age at examination. For the T2WI, there was no correlation with either the postnatal age or the gestational age at examination. CONCLUSIONS: Signal intensity on T1WI in the STN and globus pallidus is not related to the gestational age at examination; instead, signal intensities on T1WI seem to be more dependent upon the postnatal age at examination.

Fractional anisotropy--threshold dependence in tract-based diffusion tensor analysis: evaluation of the uncinate fasciculus in Alzheimer disease.

BACKGROUND AND PURPOSE: Tract-based analysis can be used to investigate required tracts extracted from other fiber tracts. However, the fractional anisotropy (FA) threshold influences tractography analysis. The current study evaluated the influence of the FA threshold in measuring diffusion tensor parameters for tract-based analysis of the uncinate fasciculus in subjects with Alzheimer disease (AD). MATERIALS AND METHODS: Subjects included 30 patients with AD and 10 healthy controls. We acquired tractographies of the uncinate fasciculus by using different FA thresholds. We measured mean FA and the apparent diffusion coefficient (ADC) along the uncinate fasciculus for different FA thresholds and evaluated the correlation between diffusion tensor parameters (FA, ADC) and the Mini-Mental State Examination (MMSE) scores. RESULTS: The uncinate fasciculus showed lower mean FA and higher mean ADC values in cases with more severe AD. A higher FA threshold led to a lower mean ADC value and a higher mean FA value along the uncinate fasciculus, whereas the relative order of measured values according to the severity of AD was not influenced by the FA threshold. An FA threshold of 0.2 showed higher correlation between mean ADC values and MMSE scores. FA thresholds of 0.15 and 0.20 showed higher correlation between mean FA values and MMSE scores. CONCLUSIONS: Appropriate selection of the FA threshold leads to higher correlation between diffusion tensor parameters and the severity of AD. For tract-based analysis of degenerative diseases such as AD, appropriate selection of the FA threshold for tractography is important.

Proteasome-mediated degradation of Tob is pivotal for triggering UV-induced apoptosis.

Eukaryotic cells respond to genotoxic stress by inducing cell growth arrest or apoptosis. Although the p53 tumor suppressor largely contributes to the response by regulating antiproliferative or pro-apoptotic genes, some genotoxic stresses including ultraviolet (UV) light induce apoptosis even in the absence of p53. The molecular mechanisms by which cells respond to UV in the p53-independent manner remain to be established. Here, we show that UV-induced stress promotes proteasome-dependent degradation of Tob, triggering an apoptotic signal. We found that Tob with either short deletion or a tag sequence at the C terminus was resistant to UV-induced degradation. Introduction of the degradation-resistant Tob impaired UV-induced apoptosis. Reciprocally, suppression of Tob by small interfering RNA (siRNA) resulted in frequent induction of apoptosis irrespective of the presence of functional p53 even at UV doses that do not promote Tob degradation. Finally, tob-deficient (tob(-/-)) mice and primary embryonic fibroblasts (MEFs) from tob(-/-) mice exhibit increased sensitivity to UV irradiation. Thus, proteasomal clearance of Tob provides a novel p53-independent pathway for UV-induced apoptosis.

Direct measurement of nitric oxide during experimental cardiopulmonary bypass.

We developed a system to measure nitric oxide (NO) concentration during cardiopulmonary bypass in anaesthetized pigs (n = 6). A T-shaped connector, attached to an NO sensor, was mounted in the extracorporeal circuit at two measuring sites: proximal to the membrane oxygenator (venous side) and distal to the arterial line filter (arterial side). After performing a preliminary validation study, we measured plasma NO concentration before and during total cardiopulmonary bypass circulation (non-pulsatile flow 1.5 l/min) and without pulmonary ventilation. After establishing bypass, PaO2 was 318 - 393 mmHg; when PaO2 was decreased to 80 - 100 mmHg, plasma NO concentration in the arterial circuit fell by 39.2 +/- 15.6 nM. There was no observable change in plasma NO concentration at the venous circuit. This new system could be useful in monitoring NO concentration during cardiac surgery with cardiopulmonary bypass, and for understanding the possible pathophysiological roles of hyper-nitric oxaemia in cardiopulmonary bypass-related cardiovascular complications.

Diurnal T2 value changes in the lumbar intervertebral discs.

AIM: To investigate if there is any in vivo diurnal T2 value changes in the nucleus pulposus in normal and degenerated lumbar intervertebral discs. MATERIALS AND METHODS: Eighteen volunteers (16 men, two women) with no symptoms related to lumbar disease were imaged in the morning before beginning daily work and in the evening after finishing work. Sagittal fast spin-echo T2-weighted images were obtained, following spin-echo transverse imaging for T2 analysis. RESULTS: The normal disc group (n=71) showed statistically significant diurnal T2 value changes (p<0.001), whilst the degenerating disc group (n=19) showed no significant diurnal changes. The normal disc group up to age 34 years showed statistically significant diurnal T2 value changes. However no significant changes were demonstrated after the age 35 years. CONCLUSION: Statistically significant diurnal T2 value changes in the normal lumbar intervertebral discs were demonstrated. Disappearance of the diurnal T2 value changes in the normal discs after the age 35 years was revealed for the first time and thought to be an aspect of aging, not caused by degeneration.

Early-onset, rapidly progressive familial tauopathy with R406W mutation.

An early-onset and rapidly progressive familial tauopathy with R406W mutation is described. The patient was a 47-year-old man who first presented with psychiatric symptoms followed by overt dementia at age 52 and died 1 year later. Postmortem study revealed tangle-associated neuronal degeneration, accentuated in the medial temporal lobe. R406W mutation was determined by sequence analysis and immunocytochemically with anti-mutant tau antibody.

Postoperative nerve conduction changes after open and endoscopic carpal tunnel release.

OBJECTIVE: To assess the improvement of motor distal latency (MDL), sensory nerve conduction velocity (SCV) of the median nerve and the amplitudes of compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) in patients with idiopathic carpal tunnel syndrome subjected to surgical treatment according to the open carpal tunnel release method and the endoscopic carpal tunnel release. METHODS: Sixty-six hands of sixty-six patients were divided into two groups: the ECTR group and the OCTR group. The patients were evaluated preoperatively, and at 1, 3, 6, and 12 months postoperatively. RESULTS: Although no statistically significant difference of the recovery of MDL and the amplitude of CMAP and SNAP was detected between the two groups at any time point during follow-up, one patient in the ECTR group in whom the operation had been converted to OCTR, showed delay of MDL and decrease in the amplitude of CMAP. CONCLUSIONS: There is a risk of nerve damage in patients undergoing ECTR. Although statistical analysis suggests that nerve conduction improves by about the same degree 12 months after ECTR or OCTR, slightly faster improvement after OCTR cannot be excluded.

Electrochemical behavior of catechol and 3,4-dihydroxytoluene in acetonitrile at a platinum-disk electrode modified with a tyrosinase containing polyacrylamide film.

A modified platinum-disk electrode coated with a non-plasticized polyacrylamide (PAA) membrane was used to study electrochemically an enzymatic reaction between tyrosinase in the PAA membrane and catechol and 3,4-dihydroxytoluene in acetonitrile (AN). Tyrosinase, a hydrophilic biofunctional material, was immobilized in the thin PAA membrane, which adhered to the platinum-disk electrode and was stable in AN. The enzymatic activity of tyrosinase in the PAA membrane to the above substrates in AN was confirmed by cyclic voltammetry and amperometry. The apparent maximum velocities (Vmaxapp) and the apparent Michaelis constants (Kmapp) were determined from the amperometric results; the apparent turnover numbers were also determined. The reduction potentials of the substrates were reported vs. the cathodic peak potential of ferrocene in AN to improve the reliability of the potential data and to make possible a comparison of the potentials in different solvents. The electrochemical system discussed in this report can be used for tracing enzymatic reactions with substrates dissolving in aprotic dipolar solvents and for investigating solvent effects on enzymatic activities.