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1.
Rev Sci Instrum ; 95(5)2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38690981

RESUMO

Helical dichroism (HD), which is defined as the difference in optical absorption between chiral pairs of lights involving left-handed (LH) and right-handed (RH) optical vortices (OVs) carrying orbital angular momentum (OAM), is a promising way to characterize chiral materials. In the current major methods of OV generation using spatial light modulators (SLMs), the speed of OAM switching is typically as slow as 100 Hz, which is comparable to low-frequency noise, making precise chiral detection difficult. Here, we theoretically propose and experimentally demonstrate a rapid modulation of the LH and RH OVs at around 50 kHz. This modulation is achieved through a rapid modulation of circularly polarized lights carrying spin angular momentum (SAM), combined with a SAM-OAM conversion technique. We establish a theory not only for rapid OV modulation but also for HD measurements using the modulated OVs. We experimentally verify the theory using helical phase holograms drawn on a SLM as a pseudo-HD active sample. Our work addresses the limitations of current methods and offers a new avenue for precise HD measurements, paving the way for the development of sensitive chiral-optical spectroscopy techniques.

2.
Oncology ; 2024 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-38237558

RESUMO

INTRODUCTION: Atezolizumab plus bevacizumab (Atez/Bev) is the preferred treatment for advanced hepatocellular carcinoma (HCC). However, biomarkers of therapeutic efficacy have remained unclear. We took a retrospective approach to explore the role of prognostic nutritional index (PNI) for predicting the outcomes of Atez/Bev treatment. METHODS: One hundred twenty-five HCC patients were enlisted; these patients received Atez/Bev treatment and underwent dynamic computerized tomography/magnetic resonance imaging to determine the treatment response on at least one occasion between October 2020 and January 2023, and their PNI before treatment and at the beginning of the second cycle (PNI-2c) was evaluated. RESULTS: During the initial evaluation, 2 (2%), 28 (22%), 70 (56%), and 25 (20%) patients exhibited a complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD), respectively. Patients with non-PD tended to have higher PNI at baseline and PNI-2c than those with PD (p = 0.245 and 0.122, respectively), with optimal baseline PNI and PNI-2c cut-off values of 42.6 and 40.4, respectively. PNI at baseline could not be used to predict overall survival (OS) or progression-free survival (PFS). However, PNI-2c predicted OS and PFS (PNI-2c ≥ 40.4 vs. < 40.4: 25.3 vs. 16.2 months, P = 0.008 for OS; 12.7 vs. 8.4 months, P = 0.036 for PFS). A multivariate analysis showed a significant association between PNI-2c and OS. CONCLUSIONS: PNI-2c is a predictor of prognosis in HCC patients treated with Atez/Bev therapy.

3.
Hepatol Res ; 53(6): 511-521, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36723964

RESUMO

AIM: Atezolizumab plus bevacizumab (Atez/Bev) therapy is expected to have good therapeutic efficacy for patients with advanced hepatocellular carcinoma (HCC). However, the clinical indicators that predict therapeutic efficacy have not been established. We retrospectively investigated whether the neutrophil-to-lymphocyte ratio (NLR) during Atez/Bev therapy could predict therapeutic efficacy. METHOD: In total, 110 patients with HCC were enrolled; they were treated with Atez/Bev therapy and evaluated for their initial response by dynamic CT or MRI at least once between October 2020 and July 2022. RESULTS: Of the 110 patients with HCC at the initial evaluation, two (2%) showed a complete response (CR), 22 (20%) partial response (PR), 62 (56%) stable disease (SD), and 24 (21%) progressive disease (PD). The NLR at the start of the second course (NLR-2c) increased from CR + PR to SD to PD. There was no significant association between the baseline NLR and the initial therapeutic response. Patients with CR + PR had lower NLR-2c values than those with SD + PD (p < 0.001) and the optimal cut-off value of NLR-2c was 1.97. Patients with NLR-2c <1.97 had better overall survival and progression-free survival (PFS) than those with NLR-2c ≥1.97 (p = 0.005 for overall survival; p < 0.001 for PFS). A multivariate analysis showed that female sex, higher PIVKA-II levels at baseline, and higher values of NLR-2c were significantly associated with poorer PFS. CONCLUSIONS: The NLR-2c value predicts the initial therapeutic response and prognosis of patients with HCC treated with Atez/Bev therapy.

4.
Hepatol Res ; 53(4): 289-300, 2023 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-36461885

RESUMO

AIM: We retrospectively investigated patients with administration of nucleos(t)ide analogs (NAs) for prevention of or against hepatitis B virus (HBV) reactivation, and their clinical outcomes after cessation of the NA. METHODS: We enrolled 180 patients who were positive for HBsAg when they started immunosuppressive therapy or chemotherapy and an NA was administered to prevent HBV reactivation (HBV carrier group), and 82 patients with resolved HBV infection who started administration of an NA after HBV reactivation (de novo HBV group). Cessation of the NA depended on each physician's judgment without definite criteria. RESULTS: A total of 27 patients in the HBV carrier group and 22 in the de novo HBV group stopped NA therapy. In the HBV carrier group, 16 patients experienced virological relapse, which was defined as HBV DNA levels ≥20 IU/ml, and one with hematological disease had an alanine aminotransferase flare after cessation of NA. Of the 16 patients, the NA was reintroduced in three, whereas, the remaining 13 had low levels of HBV DNA and no alanine aminotransferase flare. In the de novo HBV group, virological relapse occurred in six patients, and one with hematological disease had an alanine aminotransferase flare after cessation of the NA. The NA was reintroduced in four of the six patients. CONCLUSIONS: We may be able to consider to cease NA therapy proactively in HBV carriers and resolved patients with non-hematological disease, if their primary diseases are under remission after completion of immunosuppressive therapy or chemotherapy. However, careful follow up is necessary after stopping NA therapy.

5.
Jpn J Infect Dis ; 75(6): 627-630, 2022 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-35908870

RESUMO

Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first confirmed in Japan on January 15, 2020. The Fukuoka Institute of Health and Environmental Sciences conducted testing using polymerase chain reaction (PCR) for SARS-CoV-2 from January 31 to March 4, 2020. Samples (n = 119) were collected from 81 patients suspected of having SARS-CoV-2 infection, presenting with fever, cough, fatigue, pneumonia, and other symptoms; all the samples tested during that period were negative. To identify the pathogens responsible for these symptoms, we conducted multiplex PCR. Respiratory viruses, human metapneumovirus (hMPV) was detected in 10 patients (12%), human rhinovirus (HRV) in 3 patients (4%), and influenza B virus in 1 patient (1%). In addition, the patients who had the viruses were significantly older than those who did not. Infections with hMPV and HRV have been associated with a risk of severe illness and death among older adults. Therefore, differentiating SARS-CoV-2 from other respiratory viruses, such as hMPV and HRV, is necessary to prevent and control the spread of infection, especially in older adults.


Assuntos
COVID-19 , Metapneumovirus , Infecções Respiratórias , Humanos , Idoso , SARS-CoV-2 , COVID-19/diagnóstico , Japão/epidemiologia , Metapneumovirus/genética , Vírus da Influenza B , Infecções Respiratórias/diagnóstico , Infecções Respiratórias/epidemiologia
6.
J Gastroenterol Hepatol ; 37(1): 111-116, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34478173

RESUMO

BACKGROUND: We had previously reported that the administration of Gastrografin through a nasogastric tube (NGT-G) followed by long tube (LT) strategy could be a novel standard treatment for adhesive small bowel obstruction (ASBO); however, the long-term outcomes after initial improvement remain unknown. This study aimed to analyze the long-term outcomes of first-line NGT-G. METHODS: Enrolled patients with ASBO were randomly assigned to receive LT or NGT-G between July 2016 and November 2018. Thereafter, the cumulative surgery rate, cumulative recurrence rate, and overall survival (OS) rate were analyzed. In addition, subset analysis was conducted to determine the cumulative recurrence rate according to colonic contrast with Gastrografin at 24 h. RESULTS: A total of 223 patients (LT group, n = 111; NGT-G group, n = 112) were analyzed over a median follow-up duration of 550 days. The cumulative 1-year surgery rates, cumulative 1-year recurrence rates, and 1-year OS rates in the LT and NGT-G groups were 18.8% and 18.1%, 30.0% and 31.7%, and 99.1% and 96.6%, respectively; no significant differences were observed between both groups. In the NGT-G group, a negative colonic contrast at 24 h demonstrated a higher tendency for future recurrence compared with a positive colonic contrast at 24 h (1-year recurrence rate: negative contrast, 46.9% vs positive contrast, 27.6%). CONCLUSIONS: Gastrografin through a nasogastric tube followed by LT can be a promising treatment strategy for ASBO, with long-term efficacies equivalent to initial LT placement.


Assuntos
Diatrizoato de Meglumina , Obstrução Intestinal , Intubação Gastrointestinal , Meios de Contraste/administração & dosagem , Diatrizoato de Meglumina/administração & dosagem , Humanos , Obstrução Intestinal/etiologia , Obstrução Intestinal/terapia , Intestino Delgado , Aderências Teciduais/complicações , Resultado do Tratamento
7.
Sci Adv ; 6(45)2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33148646

RESUMO

Optical force is a powerful tool to actuate micromachines. Conventional approaches often require focusing and steering an incident laser beam, resulting in a bottleneck for the integration of the optically actuated machines. Here, we propose a linear nanomotor based on a plasmonic particle that generates, even when illuminated with a plane wave, a lateral optical force due to its directional side scattering. This force direction is determined by the orientation of the nanoparticle rather than a field gradient or propagation direction of the incident light. We demonstrate the arrangements of the particles allow controlling the lateral force distributions with the resolution beyond the diffraction limit, which can produce movements, as designed, of microobjects in which they are embedded without shaping and steering the laser beam. Our nanomotor to engineer the experienced force can open the door to a new class of micro/nanomechanical devices that can be entirely operated by light.

8.
J Gastroenterol ; 55(9): 858-867, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32671536

RESUMO

BACKGROUND: Gastrointestinal decompression is generally applied to a non-strangulated acute small bowel obstruction (NSASBO). Although long tube (LT) placement and administration of Gastrografin through a nasogastric tube (NGT-G) have shown advantages over NGT alone in previous studies, no studies appear to have compared LT and NGT-G. METHODS: In this multicenter, randomized controlled trial, patients with NSASBO were randomly assigned to receive LT or NGT-G between July 2016 and November 2018 at 11 Japanese institutions. The primary endpoint was non-inferiority of NGT-G compared to LT for non-surgery rate, and the lower limit of the 95% confidence interval for the non-surgery rate (-15%) was set as the lower margin for inferiority of NGT-G compared to LT. RESULTS: In total, 223 patients (LT group, n = 111; NGT-G group, n = 112) were analyzed in the present trial. The non-surgery rate was 87.4% in the LT group and 91.1% in the NGT-G group, with a 3.7% difference between NGT-G and LT (95.3%CI - 5.55 to 12.91; non-inferiority P = 0.00002923). On the other hand, the non-surgery rate with pure NGT-G alone (76.8%) that represents non-cross-over NGT-G without subsequent LT was significantly lower than that with LT (P = 0.039). Median procedure time was significantly shorter with NGT-G (1 min) than with LT (25 min; P < 0.001), whereas no significant differences in mortality or hospital stay were noted between groups. CONCLUSION: NGT-G is an effective alternative to LT as a first-line treatment for NSASBO. A sequential strategy comprising NGT-G followed by LT might offer a new standard for NSASBO. CLINICAL TRIALS REGISTRATION: This trial was registered with the University Hospital Medical Information Network Clinical Trials Registry (umin.ac.jp/ctr Identifier: UMIN000022669) prior to the start of this trial.


Assuntos
Diatrizoato de Meglumina/administração & dosagem , Obstrução Intestinal/terapia , Intestino Delgado/diagnóstico por imagem , Intubação Gastrointestinal/métodos , Idoso , Idoso de 80 Anos ou mais , Meios de Contraste/administração & dosagem , Feminino , Humanos , Obstrução Intestinal/diagnóstico por imagem , Intestino Delgado/patologia , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Radiografia/métodos
9.
Appl Spectrosc ; 74(11): 1384-1390, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32627577

RESUMO

Interactions between epitaxial graphene grown on Si- and C-faces were investigated using Raman imaging and tip-enhanced Raman scattering (TERS). In the TERS spectrum, which has a spatial resolution exceeding the diffraction limit, a D band was observed not from graphene surface, but from the edges of the epitaxial graphene ribbons without a buffer layer, which interacts with SiC on the Si-face. In contrast, for a graphene micro-island on the C-face, the D band disappeared even on the edges where the C atoms were arranged in armchair configurations. The disappearance of the edge chirality via combination between the C atoms and SiC on the C-face is responsible for this phenomenon. The TERS signals from the C-face were weaker than those from the Si-face without the buffer layer. On the Si-face with a buffer layer, the graphene TERS signal was hardly observed. TERS enhancement was suppressed by interactions on the edges or by the buffer layer between the SiC and graphene on the C- or Si-face, respectively.

10.
Sci Rep ; 10(1): 9938, 2020 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-32555405

RESUMO

In this study, surface plasmon resonance (SPR) wavelength shifts due to molecular electronic absorptions in the far-ultraviolet (FUV, < 200 nm) and deep-ultraviolet (DUV, < 300 nm) regions were investigated by attenuated total reflectance (ATR) spectroscopy. Due to the strong absorption in the DUV region, N,N-dimethylformamide (DMF) significantly increased the SPR wavelength shift of Al film. On the other hand, no such shift enhancement was observed in the visible region for Au film because DMF does not have absorbance compared to non-absorbing materials such as water and alcohols. The enhanced SPR wavelength shift, caused by the overlap between SPR and molecular resonance wavelengths in FUV-DUV region, is expected to result in high sensitivity for resonant materials.

11.
Opt Express ; 28(5): 7139-7151, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-32225948

RESUMO

In holographic data storage systems, the quality of the reconstructed data pattern is decisive and directly affects the system performance. However, noise from the optical component, electronic component and recording material deteriorates reconstruction quality. A high noise margin decoding method developed from compressed sensing technology was proposed to reduce the impact of noise in the decoding process. Compared with the conventional threshold decoding method, the proposed method is more robust to noise and more suitable for multilevel modulation. The decoding performance with five-level amplitude modulation was evaluated by both simulation and experimentation. For the combination of Gaussian noise, Rician noise and Rayleigh noise, the proposed decoding method reduces the BER of the threshold method to one-sixth with an SNR of -1 in the simulation. In the experiment, it behaves up to 8.3 times better than conventional threshold decoding.

12.
Opt Express ; 28(2): 2398-2410, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-32121930

RESUMO

We present a numerical study of optical torque between two twisted metal nanorods due to the angular momentum of the electromagnetic field emerging from their plasmonic coupling. Our results indicate that the interaction optical torque on the nanorods can be strongly enhanced by their plasmon coupling, which highly depends on not only the gap size but also the twisted angle between the nanorods. The behaviors of the optical torque are different between two plasmon coupling modes: hybridized bonding and anti-bonding modes with different resonances. The rotations of the twisted nanorods with the bonding and anti-bonding mode excitations lead to mutually parallel and perpendicular alignments, respectively. At an incident intensity of 10 mW/µm2, the rotational potential depths are more than 30 times as large as the Brownian motion energy, enabling the optical alignments with angle fluctuations less than ∼±10°. Thus, this optical alignment of the nanoparticles with the plasmon coupling allows dynamic control of the plasmonic characteristics and functions.

13.
Plant Physiol Biochem ; 142: 211-216, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31302410

RESUMO

Choline is a vital metabolite in plant and synthesized from phosphocholine by phosphocholine phosphatase. The Arabidopsis At1g17710 was identified as the first plant gene encoding the phosphatase for both phosphoethanolamine and phosphocholine (PECP) with much higher catalytic efficiency (>10-fold) for former. In betaine accumulating plants, choline is further required for betaine synthesis. In this report, we found three putative PECP genes in sugar beet, betaine accumulating plants. Two genes encode the proteins of 274 amino acid residues and designated as BvPECP1S and BvPECP2S. Another gene encodes the 331 amino acid protein (BvPECP2L) consisted of BvPECP2S with extra C-terminal amino acid. Enzymatic assays of BvPECP1S revealed that BvPECP1S exhibited the phosphatase activity for both phosphoethanolamine and phosphocholine with higher affinity (>1.8-fold) and catalytic efficiency (>2.64-fold) for phosphocholine. BvPECP2L exhibited low activity. RT-PCR experiments for BvPECP1S showed the increased expression in young leaf and root tip under salt-stress whereas the increased expression in all organs under phosphate deficiency. The expression level of BvPECP2L in salt stressed young leaf and root tip was induced by phosphate deficient. Physiological roles of BvPECP1S and BvPECP2L for the betaine synthesis were discussed.


Assuntos
Beta vulgaris/metabolismo , Monoéster Fosfórico Hidrolases/metabolismo , Proteínas de Plantas/metabolismo , Beta vulgaris/enzimologia , Beta vulgaris/genética , Beta vulgaris/fisiologia , Colina/metabolismo , Etanolaminas/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas/genética , Monoéster Fosfórico Hidrolases/genética , Filogenia , Proteínas de Plantas/genética , Proteínas Recombinantes , Estresse Salino , Alinhamento de Sequência
14.
Protoplasma ; 256(6): 1727-1736, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31342153

RESUMO

Aminotransferases catalyze the reversible pyridoxal phosphate-dependent transfer of amino groups from amino acids to oxo acids and play important roles for the balance between carbon and nitrogen metabolism. In this report, four aminotransferases (Ap1-Ap4) from a halotolerant cyanobacterium Aphanothece halophytica were examined. The results revealed that Ap1 and Ap2 exhibited the aspartate:2-oxoglutarate aminotransferase (AspAT) activity whereas Ap2 catalyzed further aminotransferase activities with alanine (AlaAT) and LL-diaminopimelate (an intermediate for the synthesis of Lys/peptidoglycan) as amino donors. Ap4 exhibited bifunctional aminotransferase with phosphoserine (PSAT) and glycine (GGAT) as amino donors. No activity was observed for Ap3. We identified third gene encoding phosphoserine phosphatase (PSP) in phosphorylate serine biosynthetic pathway. The levels of mRNA for Ap2 and ApMurE encoding UDP-N-acetylmuramoyl-L-alanyl-D-glutamate-2,6-diaminopimelate ligase were increased after salt stress. These results suggest the link among photorespiratory metabolite (serine, glycine, glyoxylate), phosphorylate serine biosynthetic pathway and aspartate metabolism via aminotransferases for the synthesis of peptidoglycan and betaine under salt stress conditions.


Assuntos
Ácido Aspártico/metabolismo , Cianobactérias/patogenicidade , Serina/metabolismo , Transaminases/metabolismo
15.
Intern Med ; 58(18): 2645-2649, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31178487

RESUMO

A 26-year-old woman complained of upper abdominal pain. Computed tomography (CT) showed acute pancreatitis, a left adrenal tumor and solitary right pulmonary metastasis. She underwent left adrenalectomy; the adrenal tumor was diagnosed as adrenocortical carcinoma (ACC). When preparing to resect the pulmonary metastasis, she suffered a second acute pancreatic attack. Magnetic resonance cholangiopancreatography (MRCP) showed that the proximal main pancreatic duct (MPD) was dilated, and the distal MPD was diminished; however, no pancreatic tumor was observed on CT or MRCP. Endoscopic ultrasonography revealed a solitary pancreatic mass, which was diagnosed as pancreatic metastasis from ACC by endoscopic ultrasonography-guided fine-needle aspiration.


Assuntos
Neoplasias do Córtex Suprarrenal/complicações , Carcinoma Adrenocortical/complicações , Biópsia por Agulha Fina/métodos , Endossonografia/métodos , Neoplasias Pancreáticas/diagnóstico , Pancreatite/diagnóstico , Doença Aguda , Adulto , Feminino , Humanos , Ductos Pancreáticos/patologia
16.
Front Plant Sci ; 10: 217, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30941150

RESUMO

Among abiotic stresses, salt stress adversely affects growth and development in rice. Contrasting salt tolerant (CSR27), and salt sensitive (MI48) rice varieties provided information on an array of genes that may contribute for salt tolerance of rice. Earlier studies on transcriptome and proteome profiling led to the identification of salt stress-induced serine hydroxymethyltransferase-3 (SHMT3) gene. In the present study, the SHMT3 gene was isolated from salt-tolerant (CSR27) rice. OsSHMT3 exhibited salinity-stress induced accentuated and differential expression levels in different tissues of rice. OsSHMT3 was overexpressed in Escherichia coli and assayed for enzymatic activity and modeling protein structure. Further, Arabidopsis transgenic plants overexpressing OsSHMT3 exhibited tolerance toward salt stress. Comparative analyses of OsSHMT3 vis a vis wild type by ionomic, transcriptomic, and metabolic profiling, protein expression and analysis of various traits revealed a pivotal role of OsSHMT3 in conferring tolerance toward salt stress. The gene can further be used in developing gene-based markers for salt stress to be employed in marker assisted breeding programs. HIGHLIGHTS: - The study provides information on mechanistic details of serine hydroxymethyl transferase gene for its salt tolerance in rice.

17.
Phys Rev E ; 99(2-1): 022119, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30934295

RESUMO

It is often regarded that the dwell time (or residence time, escape time, trapping duration) of trapped Brownian particles is described by the multiplication of two separate factors, i.e., the diffusive traveling time of the trapping domain size without taking into account the trapping force, and the stochastic event of overcoming the trapping energy by thermal one instantaneously. However, we show that the ratio of dwell time to the typical traveling time for the trapping domain size depends on the shape of the force field. The shape of the trapping potential affects this ratio even if the trapping energy gap is the same and the smooth potential has a single minimum. Our finding suggests the possible application of the potential shape to realize the desired trapping characteristics.

18.
Chem Rec ; 19(7): 1210-1219, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30256528

RESUMO

Plasmonics in the UV region has been widely focused because of the higher energy and the abundant electronic resonances compared to the conventional visible plasmonics. Recently, we have investigated the surface plasmon resonance (SPR) properties of the Al film, aiming for the application as refractive index sensors. Utilizing the UV lights, we expect three advantages: high sensitivity, material selectivity, and surface selectivity. By using an original attenuated total reflectance spectroscopic instrument, Al-SPR angle and wavelength were investigated with changing environments on the Al film. Al film thickness and materials of prisms on which Al was evaporated were also important factors for the SPR properties. By optimizing the conditions, the Al film worked as a sensor both in air and in liquids. In addition, our established system expands the plasmonics into an even higher energy region than 200 nm, while the UV-plasmonics have been studied in the wavelength region longer than 200 nm.

19.
Plant Physiol Biochem ; 127: 248-255, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29626705

RESUMO

Betaine (trimethylglycine) is an important compatible solute that accumulates in response to abiotic stresses such as drought and salinity. Biosynthetic pathways of betaine have been extensively studied, but it remains to be clarified on algae. A diatom Thalassiosira pseudonana CCMP1335 is an important component of marine ecosystems. Here we show that the genome sequence of Thalassiosira suggests the presence of two biosynthetic pathways for betaine, via three step methylation of glycine and via two step oxidation of choline. The choline oxidation via choline dehydrogenase was suggested and its sequential characteristics were analyzed. A candidate gene TpORF1 for glycine methylation encodes a protein consisted of 574 amino acids with two putative tandem repeat methyltransferase domains. The TpORF1 was expressed in E. coli, and the purified protein was shown to synthesize betaine via three step methylation of glycine and designated as TpGSDMT. The proteins containing C-terminal half or N-terminal half were expressed in E. coli and exhibited the methyl transferase activities with different substrate specificity for glycine, sarcosine and dimethylglycine. Upregulation of TpGSDMT transcription and betaine levels were observed at high salinity, suggesting the importance of TpGSDMT for salt tolerance in T. pseudonana cells.


Assuntos
Betaína , Colina , Diatomáceas/enzimologia , Genoma , Glicina , Metiltransferases , Betaína/análogos & derivados , Betaína/metabolismo , Colina/genética , Colina/metabolismo , Diatomáceas/genética , Glicina/genética , Glicina/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Metilação , Metiltransferases/química , Metiltransferases/genética , Metiltransferases/metabolismo
20.
Arch Biochem Biophys ; 645: 100-106, 2018 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-29574051

RESUMO

Dimethylsulfoniopropionate (DMSP) is one of the most abundant molecules on earth and plays a pivotal role in the marine sulfur cycle. DMSP is believed to be synthesized from methionine by a four-step reaction pathway in marine algae. The genes responsible for biosynthesis of DMSP remain unidentified. A diatom Thalassiosira pseudonana CCMP1335 is an important component of marine ecosystems and contributes greatly to the world's primary production. In this study, through genome search, in vivo activity and functional studies of cDNA products, a gene encoding Thalassiosira methyltransferase (TpMMT) which catalyzes the key step of DMSP synthesis formation of 4-methylthio-2-hydroxybutyrate (DMSHB) from 4-methylthio-2-oxobutyrate (MTHB), was identified. The amino acid sequence of TpMMT was homologous to the methyltransferase from Phaeodactylum tricornutum CCAP 1055/1, but not the recently identified bacterium gene. High salinity and nitrogen limitation stresses caused the increase of DMSP content and TpMMT protein in Thalassiosira. In addition to TpMMT, the enzyme activities for the first three steps could be detected and enhanced under high salinity, suggesting the importance of four-step DMSP synthetic pathway in Thalassiosira.


Assuntos
Diatomáceas/genética , Diatomáceas/metabolismo , Metiltransferases/genética , Metiltransferases/metabolismo , Compostos de Sulfônio/metabolismo , Sequência de Aminoácidos , Diatomáceas/efeitos dos fármacos , Diatomáceas/enzimologia , Concentração de Íons de Hidrogênio , Metionina/análogos & derivados , Metionina/metabolismo , Metiltransferases/química , Nitrogênio/farmacologia , Salinidade , Estresse Salino/genética , Temperatura , Regulação para Cima
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