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1.
Heliyon ; 10(7): e28444, 2024 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-38560205

RESUMO

Popliteal cysts, also termed Baker's cysts, are clinically common cystic lesions in the popliteal fossa. Typically, the contents of a ruptured cyst tend to spread into the myofascial interfaces in any direction, most commonly inferomedially or into a palpable superficial position. However, to our knowledge, reports of Baker's cysts dissecting into the deep intermuscular septum of the lower calf are extremely rare. We present here the details of the successful treatment through arthroscopy combined with lower calf incision of a patient who sustained hematoma of the knee and lower calf secondary to Baker's cyst rupture. Given the rarity of this disease in China, we present this case report to improve our understanding of the disease and avoid misdiagnosis and provide evidence for its clinical treatment, management, and prognosis.

2.
Redox Biol ; 72: 103129, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38574433

RESUMO

AIMS: Doxorubicin is a powerful chemotherapeutic agent for cancer, whose use is limited due to its potential cardiotoxicity. Semaglutide (SEMA), a novel analog of glucagon-like peptide-1 (GLP-1), has received widespread attention for the treatment of diabetes. However, increasing evidence has highlighted its potential therapeutic benefits on cardiac function. Therefore, the objective of this study was to examine the efficacy of semaglutide in ameliorating doxorubicin-induced cardiotoxicity. METHODS AND RESULTS: Doxorubicin-induced cardiotoxicity is an established model to study cardiac function. Cardiac function was studied by transthoracic echocardiography and invasive hemodynamic monitoring. The results showed that semaglutide significantly ameliorated doxorubicin-induced cardiac dysfunction. RNA sequencing suggested that Bnip3 is the candidate gene that impaired the protective effect of semaglutide in doxorubicin-induced cardiotoxicity. To determine the role of BNIP3 on the effect of semaglutide in doxorubicin-induced cardiotoxicity, BNIP3 with adeno-associated virus serotype 9 (AAV9) expressing cardiac troponin T (cTnT) promoter was injected into tail vein of C57/BL6J mice to overexpress BNIP3, specifically in the heart. Overexpression of BNIP3 prevented the improvement in cardiac function caused by semaglutide. In vitro experiments showed that semaglutide, via PI3K/AKT pathway, reduced BNIP3 expression in the mitochondria, improving mitochondrial function. CONCLUSION: Semaglutide ameliorates doxorubicin-induced mitochondrial and cardiac dysfunction via PI3K/AKT pathway, by reducing BNIP3 expression in mitochondria. The improvement in mitochondrial function reduces doxorubicin-mediated cardiac injury and improves cardiac function. Therefore, semaglutide is a potential therapy to reduce doxorubicin-induced acute cardiotoxicity.


Assuntos
Cardiotoxicidade , Doxorrubicina , Peptídeos Semelhantes ao Glucagon , Proteínas de Membrana , Animais , Camundongos , Cardiotoxicidade/etiologia , Cardiotoxicidade/metabolismo , Doxorrubicina/efeitos adversos , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Peptídeos Semelhantes ao Glucagon/farmacologia , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Proteínas Mitocondriais/metabolismo , Proteínas Mitocondriais/genética , Masculino , Transdução de Sinais/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Humanos
3.
J Magn Reson Imaging ; 2023 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-38006286

RESUMO

BACKGROUND: Previous studies have used different imaging sequences and different enhanced phases for breast lesion calsification in radiomics. The optimal sequence and contrast enhanced phase is unclear. PURPOSE: To identify the optimal magnetic resonance imaging (MRI) radiomics model for lesion clarification, and to simulate its incremental value for multiparametric MRI (mpMRI)-guided biopsy. STUDY TYPE: Retrospective. POPULATION: 329 female patients (138 malignant, 191 benign), divided into a training set (first site, n = 192) and an independent test set (second site, n = 137). FIELD STRENGTH/SEQUENCE: 3.0-T, fast spoiled gradient-echo and fast spin-echo T1-weighted imaging (T1WI), fast spin-echo T2-weighted imaging (T2WI), echo-planar diffusion-weighted imaging (DWI), and fast spoiled gradient-echo contrast-enhanced MRI (CE-MRI). ASSESSMENT: Two breast radiologists with 3 and 10 years' experience developed radiomics model on CE-MRI, CE-MRI + DWI, CE-MRI + DWI + T2WI, CE-MRI + DWI + T2WI + T1WI at each individual phase (P) and for multiple combinations of phases. The optimal radiomics model (Rad-score) was identified as having the highest area under the receiver operating characteristic curve (AUC) in the test set. Specificity was compared between a traditional mpMRI model and an integrated model (mpMRI + Rad-score) at sensitivity >98%. STATISTICAL TESTS: Wilcoxon paired-samples signed rank test, Delong test, McNemar test. Significance level was 0.05 and Bonferroni method was used for multiple comparisons (P = 0.007, 0.05/7). RESULTS: For radiomics models, CE-MRI/P3 + DWI + T2WI achieved the highest performance in the test set (AUC = 0.888, 95% confidence interval: 0.833-0.944). The integrated model had significantly higher specificity (55.3%) than the mpMRI model (31.6%) in the test set with a sensitivity of 98.4%. DATA CONCLUSION: The CE-MRI/P3 + DWI + T2WI model is the optimized choice for breast lesion classification in radiomics, and has potential to reduce benign biopsies (100%-specificity) from 68.4% to 44.7% while retaining sensitivity >98%. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY: Stage 2.

4.
ACS Appl Mater Interfaces ; 15(31): 37433-37441, 2023 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-37489932

RESUMO

We report a low-cost, high theoretical specific capacity π-conjugated organic compound (PTCDA) with C═O active centers as the cathode material in aluminum organic batteries. In addition, in order to improve the electron transport rate of PTCDA, a new method is proposed in this paper, which uses physical vapor deposition (PVD) method to make PTCDA recrystallize and grow on stainless steel and quartz glass substrates to improve its crystallinity. The increase of crystallinity expands the PTCDA π-π-conjugated system, making electrons more delocalized, which is beneficial to the transmission rate of electrons and ions, thereby enhancing the conductivity of the material. The experimental results show that compared with pristine PTCDA, PTCDA(Ss) and PTCDA(G) with higher crystallinity have better cycling stability and rate capability. The DFT (density functional theory) results indicated that the electron-deficient carbonyl group in the PTCDA molecule could reversibly coordinate/dissociate with the positively charged Al complex ions (AlCl2+). This research work provides insights into the rational design of low-dimensional, high-crystallinity, high-performance cathode materials for green aluminum organic batteries.

5.
J Colloid Interface Sci ; 639: 124-132, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36804785

RESUMO

Advances in cathode material design and understanding of intercalation mechanisms are necessary to improve the overall performance of aluminum ion batteries. Therefore, we designed ZnSe/SnSe2 hollow microcubes with heterojunction structure as a cathode material for aluminum ion batteries. ZnSe/SnSe2 hollow microcubes with an average size of about1.4 µm were prepared by selenization of ZnSn(OH)6 microcubes successfully. The shell thickness of ZnSe/SnSe2 hollow microcubes is about 250 nm. On one hand, the hollow cubic structure can effectively alleviate the volume effect, provide shorter ion diffusion paths, and increase the contact area with the electrolyte. On the other hand, ZnSe/SnSe2 heterojunction structure can establish a built-in electric field to facilitate ion transport. The synergistic effect of the two leads to the improved electrochemical performance of ZnSe/SnSe2 as the cathode of aluminum ion batteries. The material delivered a reversible capacity of 124 mAh/g after 150 cycles at a current density of 100 mA/g. Meanwhile, coulombic efficiency remained above 98% in almost all cycles. In addition, the electrochemical reaction mechanism and kinetic process of Al3+ and ZnSe/SnSe2 were studied.

6.
ACS Appl Mater Interfaces ; 14(48): 53702-53710, 2022 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-36413483

RESUMO

Aluminum batteries (ABs) have triggered increasing interest due to the geochemically abundant aluminum, high theoretical energy density, and excellent safety characteristics. Organic materials with engineered active groups have the advantages of low cost, flexible structural design, and benignity to the environment. Herein, we report an appropriately heat treated aromatic carbonyl derivative PTCDA/500 °C as an organic cathode material for ABs. The constructed aluminum organic batteries exhibited excellent cycling stability, with a capacity retention rate of 91% (111 mAh/g) after 200 cycles at a current density of 1000 mA/g and also displayed the more excellent rate capability at different current densities. In addition, the electrochemical reaction mechanism of AlCl2+ and PTCDA was studied based on density functional theory (DFT) as well as the ion diffusion behavior on the electrode surface being probed. The research results provide new ideas for the development of green and sustainable aluminum organic batteries.

7.
Front Bioeng Biotechnol ; 10: 938337, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35813996

RESUMO

The loosening of traditional prosthetics is among the leading causes of surgical failure of proximal femoral bone defects. A novel compound sleeve and stem prosthesis was designed using an optimization methodology that combined an octet-truss porous structure with density-based topology optimization to improve stability, promote bone ingrowth, and enhance biomechanical properties. Biomechanical changes were assessed using finite element analysis. The distribution of stress, the strain energy density, and the relative micromotion in the optimized group were considered. The optimized sleeve prosthesis achieved a 31.5% weight reduction. The maximum stresses in the optimized group were observed to decrease by 30.33 and 4.74% at the back sleeve and neck part of stem prosthesis, with a 29.52% increase in the femur, respectively. The average stress in most selected regions in the optimized group was significantly greater than that in the original group (p < 0.05). The maximum relative micromotion decreased by 15.18% (from 63.9 to 54.2 µm) in the optimized group. The novel designed compound sleeve and stem prosthesis could effectively improve the biomechanical performance of next-generation prosthetics and provide a microenvironment for bone ingrowth. The presented method could serve as a model for clinical practice and a platform for future orthopedic surgery applications.

8.
Molecules ; 27(10)2022 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-35630768

RESUMO

Polyphenolic acids are the widely occurring natural products in almost each herbal plant, among which rosmarinic acid (RA, C18H16O8) is well-known, and is present in over 160 species belonging to many families, especially the Lamiaceae. Aside from this herbal ingredient, dozens of its natural derivatives have also been isolated and characterized from many natural plants. In recent years, with the increasing focus on the natural products as alternative treatments, a large number of pharmacological studies have been carried out to demonstrate the various biological activities of RA such as anti-inflammation, anti-oxidation, anti-diabetes, anti-virus, anti-tumor, neuroprotection, hepatoprotection, etc. In addition, investigations concerning its biosynthesis, extraction, analysis, clinical applications, and pharmacokinetics have also been performed. Although many achievements have been made in various research aspects, there still exist some problems or issues to be answered, especially its toxicity and bioavailability. Thus, we hope that in the case of natural products, the present review can not only provide a comprehensive understanding on RA covering its miscellaneous research fields, but also highlight some of the present issues and future perspectives worth investigating later, in order to help us utilize this polyphenolic acid more efficiently, widely, and safely.


Assuntos
Lamiaceae , Extratos Vegetais , Cinamatos/química , Cinamatos/farmacologia , Depsídeos/química , Depsídeos/farmacologia , Humanos , Extratos Vegetais/química , Ácido Rosmarínico
9.
J Tissue Eng ; 11: 2041731420974861, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33294154

RESUMO

Natural biomaterials, such as collagen, gelatin, and chitosan, are considered as promising candidates for use in tissue regeneration treatment, given their similarity to natural tissues regarding components and structure. Nevertheless, only receiving a crosslinking process can these biomaterials exhibit sufficient strength to bear high tensile loads for use in skeletal system regeneration. Recently, genipin, a natural chemical compound extracted from gardenia fruits, has shown great potential as a reliable crosslinking reagent, which can reconcile the crosslinking effect and biosafety profile simultaneously. In this review, we briefly summarize the genipin extraction process, biosafety, and crosslinking mechanism. Subsequently, the applications of genipin regarding aiding skeletal system regeneration are discussed in detail, including the advances and technological strategies for reconstructing cartilage, bone, intervertebral disc, tendon, and skeletal muscle tissues. Finally, based on the specific pharmacological functions of genipin, its potential applications, such as its use in bioprinting and serving as an antioxidant and anti-tumor agent, and the challenges of genipin in the clinical applications in skeletal system regeneration are also presented.

10.
Med Sci Monit ; 23: 1691-1700, 2017 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-28388595

RESUMO

BACKGROUND We explored the application of 3-dimensional (3D) printing technology in treating giant cell tumors (GCT) of the proximal tibia. A tibia block was designed and produced through 3D printing technology. We expected that this 3D-printed block would fill the bone defect after en-bloc resection. Importantly, the block, combined with a standard knee joint prosthesis, provided attachments for collateral ligaments of the knee, which can maintain knee stability. MATERIAL AND METHODS A computed tomography (CT) scan was taken of both knee joints in 4 patients with GCT of the proximal tibia. We developed a novel technique - the real-size 3D-printed proximal tibia model - to design preoperative treatment plans. Hence, with the application of 3D printing technology, a customized proximal tibia block could be designed for each patient individually, which fixed the bone defect, combined with standard knee prosthesis. RESULTS In all 4 cases, the 3D-printed block fitted the bone defect precisely. The motion range of the affected knee was 90 degrees on average, and the soft tissue balance and stability of the knee were good. After an average 7-month follow-up, the MSTS score was 19 on average. No sign of prosthesis fracture, loosening, or other relevant complications were detected. CONCLUSIONS This technique can be used to treat GCT of the proximal tibia when it is hard to achieve soft tissue balance after tumor resection. 3D printing technology simplified the design and manufacturing progress of custom-made orthopedic medical instruments. This new surgical technique could be much more widely applied because of 3D printing technology.


Assuntos
Artroplastia do Joelho/instrumentação , Neoplasias Ósseas/cirurgia , Tumor de Células Gigantes do Osso/cirurgia , Impressão Tridimensional , Desenho de Prótese/métodos , Tíbia/patologia , Tíbia/cirurgia , Adulto , Feminino , Fraturas Ósseas/cirurgia , Tumores de Células Gigantes/patologia , Tumores de Células Gigantes/cirurgia , Humanos , Articulação do Joelho/patologia , Prótese do Joelho , Masculino , Pessoa de Meia-Idade , Desenho de Prótese/instrumentação , Tomografia Computadorizada por Raios X , Resultado do Tratamento
11.
Chemistry ; 22(50): 18060-18065, 2016 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-27714876

RESUMO

Two-dimensional (2D) nanomaterials are one of the most promising types of candidates for energy-storage applications due to confined thicknesses and high surface areas, which would play an essential role in enhanced reaction kinetics. Herein, a universal process that can be extended for scale up is developed to synthesise ultrathin cobalt-/nickel-based hydroxides and oxides. The sodium and lithium storage capabilities of Co3 O4 nanosheets are evaluated in detail. For sodium storage, the Co3 O4 nanosheets exhibit excellent rate capability (e.g., 179 mA h g-1 at 7.0 A g-1 and 150 mA h g-1 at 10.0 A g-1 ) and promising cycling performance (404 mA h g-1 after 100 cycles at 0.1 A g-1 ). Meanwhile, very impressive lithium storage performance is also achieved, which is maintained at 1029 mA h g-1 after 100 cycles at 0.2 A g-1 . NiO and NiCo2 O4 nanosheets are also successfully prepared through the same synthetic approach, and both deliver very encouraging lithium storage performances. In addition to rechargeable batteries, 2D cobalt-/nickel-based hydroxides and oxides are also anticipated to have great potential applications in supercapacitors, electrocatalysis and other energy-storage-/-conversion-related fields.

12.
Acta Radiol ; 56(12): 1411-8, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25422515

RESUMO

BACKGROUND: The performance of diffusion-weighted imaging parameters for characterizing hepatic tumors is controversial. PURPOSE: To compare the performances of apparent diffusion coefficient (ADC) and intravoxel incoherent motion (IVIM)-derived parameters, including the pure diffusion coefficient (D), perfusion coefficient (D*), and perfusion fraction (f), in the characterization of common solid hepatic tumors. MATERIAL AND METHODS: Twelve healthy volunteers and 43 patients underwent free-breath diffusion-weighted magnetic resonance imaging (DW-MRI) of the liver using eight b values (10-800 s/mm(2)). Twelve regions of interest (ROIs) of normal liver tissue in healthy volunteers and 49 hepatic lesions (23 hepatocellular carcinomas [HCCs], 16 hemangiomas, and 10 metastases) were measured. Conventional ADC(0,500) and ADCtotal obtained by the mono-exponential model, as well as D, D*, and f were calculated. Student t-tests and receiver operating characteristic (ROC) analysis were also performed. RESULTS: ADC(0,500), ADCtotal, and D were significantly lower in the malignant group ([1.48 ± 0.35] × 10(-3) mm(2)/s; [1.35 ± 0.30] × 10(-3) mm(2)/s; [1.18 ± 0.33] × 10(-3) mm(2)/s) compared to the hemangioma group ([2.74 ± 1.03] × 10(-3) mm(2)/s; [2.61 ± 0.81] × 10(-3) mm(2)/s; [1.97 ± 0.79] × 10(-3) mm(2)/s]. D* did not differ among multiple comparisons. For the area under the ROC curve (AUC-ROC), the maximum value was attained with ADCtotal (0.983) and was closely followed by ADC(0,500) (0.967), with lower values obtained for D (0.837), f (0.649), and D* (0.599). Statistically significant differences were found between the AUC-ROC of both ADCs (ADCtotal and ADC(0,500)) and D. There was no statistically significant difference between the AUC-ROC of ADCtotal and ADC(0,500). CONCLUSION: ADCs showed superior diagnostic performance compared to IVIM-derived parameters in detecting differences between the malignant group and hemangioma group.


Assuntos
Imagem de Difusão por Ressonância Magnética , Processamento de Imagem Assistida por Computador/métodos , Neoplasias Hepáticas/patologia , Adulto , Feminino , Humanos , Fígado/patologia , Masculino , Movimento (Física) , Curva ROC , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Adulto Jovem
13.
Sci Rep ; 4: 6095, 2014 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-25168783

RESUMO

Nano-Germanium/polypyrrole composite has been synthesized by chemical reduction method in aqueous solution. The Ge nanoparticles were directly coated on the surface of the polypyrrole. The morphology and structural properties of samples were determined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Thermogravimetric analysis was carried out to determine the polypyrrole content. The electrochemical properties of the samples have been investigated and their suitability as anode materials for the lithium-ion battery was examined. The discharge capacity of the Ge nanoparticles calculated in the Ge-polypyrrole composite is 1014 mAh g(-1) after 50 cycles at 0.2 C rate, which is much higher than that of pristine germanium (439 mAh g(-1)). The composite also demonstrates high specific discharge capacities at different current rates (1318, 1032, 661, and 460 mAh g(-1) at 0.5, 1.0, 2.0, and 4.0 C, respectively). The superior electrochemical performance of Ge-polypyrrole composite could be attributed to the polypyrrole core, which provides an efficient transport pathway for electrons. SEM images of the electrodes have demonstrated that polypyrrole can also act as a conductive binder and alleviate the pulverization of electrode caused by the huge volume changes of the nanosized germanium particles during Li(+) intercalation/de-intercalation.

14.
Urology ; 78(2): 469-73, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21664650

RESUMO

OBJECTIVES: To report a case and the surgical techniques of transperitoneal laparoscopic partial nephrectomy (LPN) in a patient with a small left renal mass and an aberrant left-sided inferior vena cava (IVC). METHODS: An otherwise healthy 49-year-old man with a body mass index of 23.1 kg/m(2) was diagnosed with a 5 × 6-cm mass in the left kidney. A transperitoneal LPN was performed in the presence of a left-sided IVC. The procedure was completed using standard laparoscopic instruments. The left renal vein was identified, with the gonadal vein used as an anatomic landmark. Slightly rostral to the location where the renal vein emptied into the left-sided IVC, 2 renal arteries were dissected and clamped individually using laparoscopic bulldog clamps. A standard LPN was then completed. RESULTS: The duration of the surgery was 182 minutes, and there was an estimated blood loss of 100 mL. The warm ischemic time was 31 minutes. The postoperative recovery was uneventful, and the patient was discharged to his home on postoperative day 7. A pathologic examination revealed a renal oxyphilic adenoma, which is a benign lesion. At the follow-up visits that were 1 month and 3 months after surgery, the patient was determined to be clinically healthy. CONCLUSIONS: The anomaly of a left-sided IVC is not an impediment to performing a transperitoneal LPN; however, the correct identification of the anatomical landmarks and the use of meticulous intraoperative techniques are of paramount importance during this procedure.


Assuntos
Neoplasias Renais/complicações , Neoplasias Renais/cirurgia , Laparoscopia , Nefrectomia/métodos , Veia Cava Inferior/anormalidades , Humanos , Masculino , Pessoa de Meia-Idade , Peritônio
15.
Biochemistry ; 48(27): 6361-8, 2009 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-19489611

RESUMO

The dynamic and structural properties of membrane proteins are intimately affected by the lipid bilayer. One property of membrane proteins is uniaxial rotational diffusion, which depends on the membrane viscosity and thickness. This rotational diffusion is readily manifested in solid-state NMR spectra as characteristic line shapes and temperature-dependent line narrowing or broadening. We show here that this whole-body uniaxial diffusion is suppressed in lipid bilayers mimicking the composition of eukaryotic cell membranes, which are rich in cholesterol and sphingomyelin. We demonstrate this membrane-induced immobilization on the transmembrane peptide of the influenza A M2 (AM2-TM) proton channel protein. At physiological temperature, AM2-TM undergoes uniaxial diffusion faster than approximately 10(5) s(-1) in DLPC, DMPC, and POPC bilayers, but the motion is slowed by 2 orders of magnitude, to <10(3) s(-1), in a cholesterol-rich virus envelope-mimetic membrane ("viral membrane"). The immobilization is manifested as near rigid-limit (2)H quadrupolar couplings and (13)C-(1)H, (15)N-(1)H, and (13)C-(15)N dipolar couplings for all labeled residues. The immobilization suppresses intermediate time scale broadening of the NMR spectra, thus allowing high-sensitivity and high-resolution spectra to be measured at physiological temperature. The conformation of the protein in the viral membrane is more homogeneous than in model PC membranes, as evidenced by the narrow (15)N lines. The immobilization of the M2 helical bundle by the membrane composition change indicates the importance of studying membrane proteins in environments as native as possible. It also suggests that eukaryote-mimetic lipid membranes may greatly facilitate structure determination of membrane proteins by solid-state NMR.


Assuntos
Bicamadas Lipídicas , Mimetismo Molecular , Ressonância Magnética Nuclear Biomolecular/métodos , Proteínas do Envelope Viral/química , Proteínas da Matriz Viral/química , Colesterol/análise , Esfingomielinas/análise
16.
J Phys Chem B ; 111(36): 10825-32, 2007 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-17705425

RESUMO

The M2 transmembrane peptide (M2TMP) of the influenza A virus forms a tetrameric helical bundle that acts as a proton-selective channel important in the viral life cycle. The side-chain conformation of the peptide is largely unknown and is important for elucidating the proton-conducting mechanism and the channel stability. Using a 19F spin diffusion NMR technique called CODEX, we have measured the oligomeric states and interhelical side chain-side chain 19F-19F distances at several residues using singly fluorinated M2TMP bound to DMPC bilayers. 19F CODEX data at a key residue of the proton channel, Trp41, confirm the tetrameric state of the peptide and yield a nearest-neighbor interhelical distance of approximately 11 A under both neutral and acidic pH. Since the helix orientation is precisely known from previous 15N NMR experiments and the backbone channel diameter has a narrow allowed range, this 19F distance constrains the Trp41 side-chain conformation to t90 (chi1 approximately 180 degrees , chi2 approximately 90 degrees ). This Trp41 rotamer, combined with a previously measured 15N-13C distance between His37 and Trp411, suggests that the His37 rotamer is t-160. The implication of the proposed (His37, Trp41) rotamers to the gating mechanism of the M2 proton channel is discussed. Binding of the antiviral drug amantadine to the peptide does not affect the F-F distance at Trp41. Interhelical 19F-19F distances are also measured at residues 27 and 38, each mutated to 4-19F-Phe. For V27F-M2TMP, the 19F-19F distances suggest a mixture of dimers and tetramers, whereas the L38F-M2TMP data indicate two tetramers of different sizes, suggesting side chain conformational heterogeneity at this lipid-facing residue. This work shows that 19F spin diffusion NMR is a valuable tool for determining long-range intermolecular distances that shed light on the mechanism of action and conformational heterogeneity of membrane protein oligomers.


Assuntos
Vírus da Influenza A/química , Canais Iônicos/química , Peptídeos/química , Proteínas da Matriz Viral/química , Flúor/química , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Conformação Proteica , Prótons , Triptofano/química
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