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1.
J Phys Chem B ; 128(23): 5727-5734, 2024 Jun 13.
Article in English | MEDLINE | ID: mdl-38832921

ABSTRACT

The structure H (sH) of methane hydrate, which has a distinctive structure with large (LL) cages capable of encapsulating multiple methane molecules, has been suggested as a methane reservoir in large icy bodies such as Titan, making it important in planetary science. This high-pressure phase, which exists in the GPa range, lends itself to the study of methane states and dynamics using powerful experimental techniques such as IR and Raman spectroscopy. However, the interpretation of the vibrational spectra of methane in the sH structure has been challenging because of the spectral complexities. The signals attributed to the methane molecules in the LL cage, as well as those of the other two cage types, overlap in the spectra. In this study, we investigated the microscopic origins of the shape of the C-H stretching vibration spectrum of methane in the LL cage using ab initio molecular dynamics (AIMD) simulations. For a single methane molecule in the LL cage, the ν3 band of the C-H stretching mode was observed at a higher frequency typical of isolated molecules in vacuum due to the large size of the LL cage. As the number of methane molecules in the LL cage increased beyond one, a tendency to blue-shift with increasing methane occupancy was observed, consistent with a loose-cage-tight-cage model. By characterizing the time correlation function of methane stretching vibrations based on the solvation number of methane and water molecules proximal to methane within the LL cage, we showed that the complicated spectral line shape observed in cases of higher methane occupancy in the LL cage resulted from the wider variation of the solvation shell states. Analysis of the solvation structures of the AIMD trajectories provided interpretations of the experimental spectral line shape, demonstrating the complementary nature of AIMD to the experiment and its effectiveness in analysis.

2.
Neuropathology ; 2024 Mar 13.
Article in English | MEDLINE | ID: mdl-38477051

ABSTRACT

Since the World Health Organization (WHO) 2016 revision, the number of molecular markers required for diffuse gliomas has increased, placing a burden on clinical practice. We have established an in-house, molecular diagnostic platform using Senshin-Iryo, a feature of Japan's unique healthcare system, and partially modified the analysis method in accordance with the WHO 2021 revision. Herein, we review over a total 5 years of achievements using this platform. Analyses of IDH, BRAF, and H3 point mutations, loss of heterozygosity (LOH) on 1p/19q and chromosomes 10 and 17, and MGMT methylation were combined into a set that was submitted to Senshin-Iryo as "Drug resistance gene testing for anticancer chemotherapy" and was approved in August 2018. Subsequently, in October 2021, Sanger sequencing for the TERT promoter mutation was added to the set, and LOH analysis was replaced with multiplex ligation-dependent probe amplification (MLPA) to analyze 1p/19q codeletion and newly required genetic markers, such as EGFR, PTEN, and CDKN2A from WHO 2021. Among the over 200 cases included, 54 were analyzed after the WHO 2021 revision. The laboratory has maintained a diagnostic platform where molecular diagnoses are confirmed within 2 weeks. Initial expenditures exceeded the income from patient copayments; however, it has gradually been reduced to running costs alone and is approaching profitability. After the WHO 2021 revision, diagnoses were confirmed using molecular markers obtained from Senshin-Iryo in 38 of 54 cases (70.1%). Among the remaining 16 patients, only four (7.4%) were diagnosed with diffuse glioma, not elsewhere classified, which was excluded in 12 cases where glioblastoma was confirmed by histopathological diagnosis. Our Senshin-Iryo trial functioned as a salvage system to overcome the transition period between continued revisions of WHO classification that has caused a clinical dilemma in the Japanese healthcare system.

3.
Phys Chem Chem Phys ; 25(33): 22161-22170, 2023 Aug 23.
Article in English | MEDLINE | ID: mdl-37564022

ABSTRACT

The pressure-induced amorphization (PIA) of ice and clathrate hydrates occurs at temperatures significantly below their melting and decomposition points. The PIA of type I clathrate hydrates containing methane and ethane as guest molecules was investigated using Raman and infrared (IR) spectroscopy. With isothermal compression at 100 K, methane hydrate (MH) underwent PIA at 2-3.5 GPa, whereas ethane hydrate (EH) underwent PIA at 4.0-5.5 GPa. The type I clathrate structure consists of small (512) and large (51262) cages. The Raman results revealed that the collapsed small and large cages in the amorphous forms of MH and EH were not distinguishable. The collapsed cages, including the methane and ethane molecules, were similar to the small and large cages, respectively. Their water networks were folded or expanded during the PIA process so that the cavity sizes of the collapsed cages were compatible with those of the guest molecules. Peaks in the IR spectra of crystalline MH assignable to the ro-vibrational transition of methane in large cages were observed in the C-H stretching wavenumber region below 40 K. The ro-vibrational IR band disappeared after amorphization, suggesting that the rotational motion of the methane molecule in the large cage was frozen by the collapse, as reported in previous dielectric spectroscopic and simulation studies. This study contributes to a better understanding of the changes in the local structure around guest molecules during PIA and the dynamics of the guest molecules.

4.
Neurooncol Adv ; 5(1): vdad078, 2023.
Article in English | MEDLINE | ID: mdl-37528810

ABSTRACT

Background: Telomerase reverse transcriptase promoter (TERTp) mutations are a biological marker of glioblastoma; however, the prognostic significance of TERTp mutational status is controversial. We evaluated this impact by retrospectively analyzing the outcomes of patients with isocitrate dehydrogenase (IDH)- and TERTp-wild-type glioblastomas. Methods: Using custom next-generation sequencing, we analyzed 208 glioblastoma samples harboring wild-type IDH. Results: TERTp mutations were detected in 143 samples (68.8%). The remaining 65 (31.2%) were TERTp-wild-type. Among the TERTp-wild-type glioblastoma samples, we observed a significant difference in median progression-free survival (18.6 and 11.4 months, respectively) and overall survival (not reached and 15.7 months, respectively) in patients with and without phosphatase and tensin homolog (PTEN) loss and/or mutation. Patients with TERTp-wild-type glioblastomas with PTEN loss and/or mutation were younger and had higher Karnofsky Performance Status scores than those without PTEN loss and/or mutation. We divided the patients with TERTp-wild-type into 3 clusters using unsupervised hierarchical clustering: Good (PTEN and TP53 alterations; lack of CDKN2A/B homozygous deletion and platelet-derived growth factor receptor alpha (PDGFRA) alterations), intermediate (PTEN alterations, CDKN2A/B homozygous deletion, lack of PDGFRA, and TP53 alterations), and poor (PDGFRA and TP53 alterations, CDKN2A/B homozygous deletion, and lack of PTEN alterations) outcomes. Kaplan-Meier survival analysis indicated that these clusters significantly correlated with the overall survival of TERTp-wild-type glioblastoma patients. Conclusions: Here, we report that PTEN loss and/or mutation is the most useful marker for predicting favorable outcomes in patients with IDH- and TERTp-wild-type glioblastomas. The combination of 4 genes, PTEN, TP53, CDKN2A/B, and PDGFRA, is important for the molecular classification and individual prognosis of patients with IDH- and TERTp-wild-type glioblastomas.

5.
Sci Rep ; 13(1): 10497, 2023 06 28.
Article in English | MEDLINE | ID: mdl-37380755

ABSTRACT

Glioblastoma, a malignant tumor, has no curative treatment. Recently, mitochondria have been considered a potential target for treating glioblastoma. Previously, we reported that agents initiating mitochondrial dysfunction were effective under glucose-starved conditions. Therefore, this study aimed to develop a mitochondria-targeted treatment to achieve normal glucose conditions. This study used U87MG (U87), U373, and patient-derived stem-like cells as well as chloramphenicol (CAP) and 2-deoxy-D-glucose (2-DG). We investigated whether CAP and 2-DG inhibited the growth of cells under normal and high glucose concentrations. In U87 cells, 2-DG and long-term CAP administration were more effective under normal glucose than high-glucose conditions. In addition, combined CAP and 2-DG treatment was significantly effective under normal glucose concentration in both normal oxygen and hypoxic conditions; this was validated in U373 and patient-derived stem-like cells. 2-DG and CAP acted by influencing iron dynamics; however, deferoxamine inhibited the efficacy of these agents. Thus, ferroptosis could be the underlying mechanism through which 2-DG and CAP act. In conclusion, combined treatment of CAP and 2-DG drastically inhibits cell growth of glioblastoma cell lines even under normal glucose conditions; therefore, this treatment could be effective for glioblastoma patients.


Subject(s)
Ferroptosis , Glioblastoma , Humans , Glioblastoma/drug therapy , Chloramphenicol/pharmacology , Glucose , Deoxyglucose/pharmacology
6.
Angew Chem Int Ed Engl ; 62(24): e202304132, 2023 Jun 12.
Article in English | MEDLINE | ID: mdl-37041112

ABSTRACT

The total synthesis of lucidumone (1), a Ganoderma meroterpenoid, was accomplished in racemic form from easily prepared 6 and 7 in 10 steps as the longest linear sequence. The synthesis was completed through one-pot preparation of the tetracyclic core skeleton by Claisen rearrangement followed by an intramolecular aldol reaction. The intramolecular aldol reaction allowed for the stereocontrolled construction of the bicyclo [2.2.2] octane skeleton fused to an indanone structure. The enantioselective total synthesis of 1 was also described via a chiral transfer strategy in the Claisen rearrangement.

7.
Br J Neurosurg ; 37(3): 457-459, 2023 Jun.
Article in English | MEDLINE | ID: mdl-31208256

ABSTRACT

Tissue diagnosis of brain tumours in eloquent is often done via needle biopsy but this method yields small samples that may not be representative of the whole tumour. The Neuroport® system enables a larger tumour biopsy to be taken via a burr hole. We report our experience on 5 cases October 2017 and June 2018. Brainlab® navigation was used. The diagnosis in all patients was made without worsening of their modified Rankin scale scores.


Subject(s)
Brain Neoplasms , Humans , Biopsy , Brain Neoplasms/diagnosis , Brain Neoplasms/surgery , Brain Neoplasms/pathology , Trephining , Magnetic Resonance Imaging , Brain/surgery , Brain/pathology
8.
Cancers (Basel) ; 14(5)2022 Feb 28.
Article in English | MEDLINE | ID: mdl-35267565

ABSTRACT

This study aimed to evaluate the efficacy and safety of computed tomography-magnetic resonance imaging (CT-MRI)-guided multi-catheter interstitial brachytherapy for patients with bulky (≥4 cm) and high-risk, stage IIB-IVB advanced cervical cancer. Eighteen patients who underwent concurrent chemoradiotherapy with multi-catheter interstitial brachytherapy between September 2014 and August 2020 were enrolled. The prescribed dose of external beam radiotherapy was 45-50.4 Gy, and the brachytherapy high-dose-rate aim was 25-30 Gy per 5 fractions. The endpoints were four-year local and pelvic control rates, four-year disease-free and overall survival rates, and the adverse events rate. The median follow-up period was 48.4 months (9.1-87.5 months). Fifteen patients received concurrent cisplatin therapy (40 mg/m2, q1week). Four (22.2%), seven (38.9%), and seven (38.9%) patients had stage II, III, and IV cervical cancer, respectively. Pelvic and para-aortic lymph node metastases were observed in 11 (61.1%) and 2 (11.1%) patients, respectively. The median pre-treatment volume was 87.5 cm3. The four-year local control, pelvic control, disease-free survival, and overall survival rates were 100%, 100%, 81.6%, and 87.8%, respectively. Three (16.7%) patients experienced grade 3 adverse events, and none experienced grade 4-5 adverse events. CT-MRI-guided multi-catheter interstitial brachytherapy could be a promising treatment strategy for locally advanced cervical cancer.

9.
ESC Heart Fail ; 8(3): 1767-1774, 2021 06.
Article in English | MEDLINE | ID: mdl-33838022

ABSTRACT

AIMS: Functional decline is associated with worse outcomes in patients with elderly heart failure (HF), but little is known about the prognostic impact of hospital-acquired disability (HAD) during hospital stay after acute HF. The present study examines the prognostic significance of HAD in the prediction of all-cause mortality in elderly patients who admitted for acute HF. METHODS AND RESULTS: This retrospective study was performed in 1941 elderly patients aged ≥65 years or older from the cardiovascular physiotherapy for acute HF patients in the Tokyo metropolitan area registry and excluded those who died in hospital. HAD was defined as any decline in the Barthel index (BI) before discharge compared with the BI within 1 month before hospital admission. The primary outcome of this study was all-cause death and HF readmission. A total of 565 (29%) deaths and 789 (41%) HF readmission occurred over a median follow-up period of 1.7 years. A total of 476 patients (25%) had HAD during hospital stay after acute HF. In multivariable analysis, HAD predicted all-cause death [hazard ratio (HR): 1.772; 95% confidence interval (CI): 1.450-2.167; P < 60; 0.001] and with risk of HF readmission (HR: 1.193; 95% CI: 1.005-1.416; P = 0.043) after adjusting for the Meta-analysis Global Group in Chronic Heart Failure risk score. CONCLUSIONS: Hospital-acquired disability is associated with an increased risk of all-cause death and readmission for HF in elderly patients with acute HF.


Subject(s)
Heart Failure , Patient Readmission , Aged , Heart Failure/epidemiology , Hospitals , Humans , Prognosis , Prospective Studies , Retrospective Studies
10.
Intern Med ; 60(9): 1451-1456, 2021 May 01.
Article in English | MEDLINE | ID: mdl-33281156

ABSTRACT

While aspiration pneumonia constitutes the majority of pneumonia cases in the elderly, it remains highly underdiagnosed. We experienced a case of recurrent pneumonia and chronic cough that was later diagnosed as aspiration pneumonia and diffuse aspiration bronchiolitis (DAB) due to recurrent hemorrhaging from an intramedullary cavernous malformation. The patient was finally diagnosed when life-threatening respiratory depression caused emergency attention. This is the first report of hemorrhaging from an intramedullary cavernous malformation diagnosed due to aspiration pneumonia and DAB. These findings highlight the importance of considering aspiration in cases with recurrent pneumonia or chronic cough. The underlying cause may be a life-threatening condition.


Subject(s)
Bronchiolitis , Deglutition Disorders , Pneumonia, Aspiration , Pneumonia , Aged , Chronic Disease , Cough/etiology , Humans
11.
J Radiat Res ; 61(3): 506-510, 2020 May 22.
Article in English | MEDLINE | ID: mdl-32266411

ABSTRACT

The present study aimed to report the efficacy and toxicity of our high-dose-rate (HDR) brachytherapy for early stage lip cancer (LC) using customized dental spacers. A retrospective analysis was performed among six patients with early stage LC treated with HDR interstitial brachytherapy between April 2015 and August 2019 using customized dental spacers. The total treatment dose was 49 Gy/7 fractions or 54 Gy/9 fractions. The median follow-up duration for the patients was 13 (range: 2-52) months. All patients completed the entire brachytherapy protocol safely and have experienced no local recurrence thus far. The CTV D100 and D90 values per fraction were median 100 (range: 98.3-100) % prescribed dose (PD) and median 133.4 (range: 129.3-138.9) % PD, respectively. The D2cc and D0.1cc values per fraction for the mandible were median 1.07 (range, 0.79-1.88) Gy and median 1.65 (range: 1.21-2.83) Gy, D2cc and D0.1cc values per fraction for oral cavity were median 1.48 (range, 1.31-1.72) Gy and median 2.73 (range: 1.79-2.88) Gy, respectively. Acute toxicities encountered were mucositis and lip edema limited to the irradiated area; none of them was beyond grade 2 and all were resolved within 1-2 months after treatment. We did not observe any late grade 2 adverse events or worse. This study shows that the adverse effects of HDR brachytherapy for early stage LC can be minimized using a dental spacer. Cooperation with the dentistry department is essential to make spacers that are individually customized for each patient.


Subject(s)
Brachytherapy/instrumentation , Brachytherapy/methods , Carcinoma, Squamous Cell/radiotherapy , Lip Neoplasms/radiotherapy , Mouth Protectors , Radiation Protection/methods , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Neoplasm Recurrence, Local , Radiotherapy Dosage , Retrospective Studies
12.
J Neuroendovasc Ther ; 14(7): 268-272, 2020.
Article in English | MEDLINE | ID: mdl-37502617

ABSTRACT

Objective: We present a case of subarachnoid hemorrhage (SAH) due to ruptured mycotic aneurysm found in the distal superior cerebellar artery (SCA). Case Presentation: A 64-year-old man was admitted to our hospital with sudden unconsciousness. He had a history of alcoholism but no family history of SAH. Computed tomography (CT) showed apparent SAH; however, CT angiography (CTA) showed no apparent cause of SAH except for two small aneurysms in the same branch of the left distal SCA. We suspected mycotic aneurysm and prescribed antibiotics. It was difficult to diagnose the condition as mycotic aneurysm because there were no vegetations or caries at the time of admission. Because there were two aneurysms in the same branch with partial dilatation and stenosis, we suspected dissecting aneurysm, but continued to administer antibiotics for possible mycotic aneurysm. After the first operation, we diagnosed mycotic aneurysm because a vegetation and valve degeneration was found. Conclusion: It is difficult to distinguish mycotic aneurysms from dissecting aneurysms because of similar appearance on imaging, especially if no vegetation is found. Nevertheless, it is important to start treatment for mycotic aneurysm. If there is the possibility of mycotic aneurysm, appropriate antibiotics should be administered, and endovascular treatment could be considered for patients with deteriorating conditions.

13.
J Stroke Cerebrovasc Dis ; 29(3): 104585, 2020 Mar.
Article in English | MEDLINE | ID: mdl-31883791

ABSTRACT

BACKGROUND: Many known risk factors, including hypertension and hyperlipidemia cause intracerebral hemorrhage (ICH). Recently, microbleeds have been identified as one of the factors leading to ICH. While some patients have been found to have recurrent ICH, risk factors for recurrent ICH are scarcely reported. We conducted an observational study on the risk-factors of recurrent ICH, comparing stroke patients with a single hemorrhagic episode and those with recurrent ICH. METHODS: A retrospective analysis of a single-center database was performed to analyze the clinical presentation and characteristics of patients with a single and recurrent ICH. From January 2016 to December 2017, a total of 317 patients were analyzed based on suspected factors including patients' sex, age, medical history, antiplatelet therapy use, and presence of microbleeds on images. RESULTS: Of the 317 patients, 36 patients (11.4%) developed a second episode of cerebral hemorrhage. Brain magnetic resonance imaging (MRI) of the patients without microbleeds, predicted reduced risk of recurrence. This is the first report strongly associating the presence of microbleeds with the possibility of a recurrent ICH. Other factors under study did not show an apparent association with recurrent ICH probably because of the high statistical significance obtained with the presence of microbleeds. CONCLUSION: Our findings revealed that the absence of microbleeds on images is a factor that strongly predicts a reduced risk for recurrent ICH and that the detection of microbleeds on MRI performed in patients with a single hemorrhagic episode, is useful in defining further therapeutic management. These findings may benefit physicians treating stroke patients.


Subject(s)
Cerebral Hemorrhage/diagnostic imaging , Magnetic Resonance Imaging , Aged , Aged, 80 and over , Cerebral Hemorrhage/therapy , Databases, Factual , Female , Humans , Male , Middle Aged , Predictive Value of Tests , Prognosis , Recurrence , Retrospective Studies , Risk Assessment , Risk Factors , Time Factors
14.
NMC Case Rep J ; 6(4): 101-103, 2019 Oct.
Article in English | MEDLINE | ID: mdl-31592396

ABSTRACT

Trigeminal neuralgia is caused by compression of the trigeminal nerve by arteries or veins in the posterior fossa. A persistent primitive trigeminal artery variant (PPTAv) is an anomalous artery that may cause trigeminal neuralgia. A 65-year-old man presented with left facial pain. Brain magnetic resonance imaging revealed a PPTAv. Constructive interference in steady state showed that both the PPTAv and the superior cerebellar artery (SCA) compressed the trigeminal nerve. Thus, we performed microvascular decompression and the patient's symptoms improved. PPTAv is a rare anomaly in the posterior fossa that can cause trigeminal neuralgia. Dual compression of the trigeminal nerve by the SCA and PPTAv demonstrates that trigeminal neuralgia may originate from multiple sources. It is therefore important to check preoperative images to adequately treat trigeminal neuralgia.

15.
World Neurosurg ; 127: 442-445, 2019 Jul.
Article in English | MEDLINE | ID: mdl-31029823

ABSTRACT

BACKGROUND: The incidence of penetrating intracranial foreign bodies is rare, and to date, not many relevant studies have been published worldwide. In particular, a nail penetrating intracranially, just near the superior sagittal sinus (SSS), is extremely rare. We treated the case of a large nail that penetrated the middle of the head and strategized its removal. CASE DESCRIPTION: A 70-year-old man had experienced headache lasting a day. Computed tomography of the brain revealed a nail penetrating the middle of his head; in particular, the tip of the nail had penetrated the right ventricle, causing a slight subarachnoid hemorrhage. Angiography showed that the nail was very close to the SSS and that the venous flow was normal. However, there was a risk of the nail penetrating through the SSS or injuring other arteries, and we removed the nail directly from the intracranial view to stop bleeding from the SSS or other vessels. Fortunately, there was no bleeding, and we washed the hole created by the nail penetration and concluded the surgery. CONCLUSIONS: Our technique is useful and safe for removing large nails penetrating the head.


Subject(s)
Brain/diagnostic imaging , Foreign Bodies/surgery , Head Injuries, Penetrating/surgery , Suicide, Attempted , Aged , Craniotomy/methods , Foreign Bodies/diagnostic imaging , Head Injuries, Penetrating/diagnostic imaging , Humans , Male , Subarachnoid Hemorrhage, Traumatic/diagnostic imaging , Subarachnoid Hemorrhage, Traumatic/etiology , Subarachnoid Hemorrhage, Traumatic/surgery , Tomography, X-Ray Computed
16.
J Chem Phys ; 144(23): 234503, 2016 Jun 21.
Article in English | MEDLINE | ID: mdl-27334175

ABSTRACT

The self-diffusion of ice VII in the pressure range of 5.5-17 GPa and temperature range of 400-425 K was studied using micro Raman spectroscopy and a diamond anvil cell. The diffusion was monitored by observing the distribution of isotope tracers: D2O and H2 (18)O. The diffusion coefficient of hydrogen reached a maximum value around 10 GPa. It was two orders of magnitude greater at 10 GPa than at 6 GPa. Hydrogen diffusion was much faster than oxygen diffusion, which indicates that protonic diffusion is the dominant mechanism for the diffusion of hydrogen in ice VII. This mechanism is in remarkable contrast to the self-diffusion in ice Ih that is dominated by an interstitial mechanism for the whole water molecule. An anomaly around 10 GPa in ice VII indicates that the rate-determining process for the proton diffusion changes from the diffusion of ionic defects to the diffusion of rotational defects, which was suggested by proton conductivity measurements and molecular dynamics simulations.

17.
Rev Sci Instrum ; 87(12): 125107, 2016 Dec.
Article in English | MEDLINE | ID: mdl-28040931

ABSTRACT

A new cooling system using Peltier modules is presented for a low-temperature diamond anvil cell instrument. This cooling system has many advantages: it is vibration-free, low-cost, and compact. It consists of double-stacked Peltier modules and heat sinks, where a cooled ethylene glycol-water mixture flows through a chiller. Current is applied to the Peltier modules by two programmable DC power supplies. Sample temperature can be controlled within the range 210-300 K with a precision of ±0.1 K via a Proportional-Integral-Differential (PID) control loop. A Raman spectroscopic study for the H2O ice VII-VIII transition is shown as an example of an application of the Peltier cooling diamond anvil cell system.

18.
J Chem Phys ; 141(8): 084306, 2014 Aug 28.
Article in English | MEDLINE | ID: mdl-25173013

ABSTRACT

Oligomerization of benzene at high pressures up to 16 GPa was investigated at room temperature using an opposed-anvil type pressure apparatus. The recovered samples were analyzed using GC-MS to identify and quantify the products after the high-pressure experiments. Some structural isomers of benzene dimer as well as biphenyl, naphthalene, and terphenyl isomers were detected at pressures higher than 13 GPa. The molar yield of the polycyclic aromatic hydrocarbons increased concomitantly with increasing pressure, although benzene still remained. The oligomerization is likely to occur when the neighbor distance of the benzene molecules exceeds the threshold of the reaction distance. The oligomerization is regarded as a precursory phenomenon of the amorphization that occurs at higher pressure.

19.
Spectrochim Acta A Mol Biomol Spectrosc ; 133: 509-13, 2014 Dec 10.
Article in English | MEDLINE | ID: mdl-24975636

ABSTRACT

The nature of protons in ice VII up to 368°C and 16GPa was investigated with synchrotron near-infrared spectroscopy. The absorption band of the first OH stretching overtone mode divided into doublet peaks above 5GPa at room temperature, suggesting that proton tunneling occurs at the overtone level. As the temperature increased, the doublet peaks gradually reduced to a singlet. This result implies that thermally activated protons hop between the two potential minima along the oxygen-oxygen axis. A pressure-temperature diagram for the proton state was constructed from the changing band shape of the overtone mode.


Subject(s)
Protons , Spectroscopy, Near-Infrared , Water/chemistry , Hot Temperature , Ice/analysis , Pressure
20.
J Phys Chem A ; 113(29): 8169-75, 2009 Jul 23.
Article in English | MEDLINE | ID: mdl-19569705

ABSTRACT

Photodissociation spectroscopy of solvated clusters of protonated tryptophan (TrpH(+)) and dipeptides containing tryptophan (Val-TrpH(+), Ala-TrpH(+), and Gly-TrpH(+)) has been carried out at low temperature to investigate the protonation and solvation effects on the electronic spectrum. For the protonated dipeptides, the S(1)-S(0) transition exhibits a substantial red shift due to the stronger interaction between the NH(3)(+) group and the indole pi ring. The S(1)-S(0) spectra of TrpH(+)(CH(3)OH)(n) clusters exhibit a drastic change with the number of methanol molecules. This behavior is interpreted in terms of the decrease in the interaction between the pi pi* and the repulsive pi sigma* states. Ala-TrpH(+) and Gly-TrpH(+) exhibit an extensive spectral change with addition of two methanol molecules. This change is ascribed to a conformational change, which is induced by the insertion of solvent molecule in between the NH(3)(+) group and the indole pi ring.


Subject(s)
Dipeptides/chemistry , Electrons , Protons , Solvents/chemistry , Tryptophan/chemistry , Models, Molecular , Protein Conformation , Spectrophotometry, Ultraviolet , Temperature
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