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1.
Heliyon ; 9(5): e16319, 2023 May.
Artículo en Inglés | MEDLINE | ID: mdl-37251873

RESUMEN

Calla lily (Zantedeschia aethiopica (L.) Spreng.) is an important ornamental crop used in garden landscapes, floral arrangements, and medicinal applications. Gibberellic acid (GA3) is actively involved in cell elongation, growth, physiology, and flowering. In addition, it is an environmentally-friendly compound which can be applied to plants to increase the ornamental production. Therefore, the present study was designed with three GA3 spray times viz., single, double and triple spray and five exogenous applications of gibberellic acid concentrations viz., 0, 25, 50, 100, and 200 mg L-1 with factorial randomized block design. Results revealed that the interaction effect of combinations of two time applications of GA3 at 100 mg L-1 induced higher growth parameters over control. Significantly higher physiological parameters viz., photosynthetic rate (14.3 µmol m-2s-1), number of stomata (26.5 mm-2), stomatal conductance (0.28 mmol m-2s-1), and transpiration rate (3.6 mmol m-2s-1) were reported when plants were treated twice with 100 mg L-1 GA3. Similarly, among flowering traits, days to flower were significantly low in plants treated two-time spray at GA3 100 mg L-1 (169.8 days). The number of flowers in the double spray at GA3 100 mg L-1 treatment increased by 11.3 and 23.7% over triple spray and control, respectively. Vase life was also significantly higher in plants treated with double spray at GA3 100 mg L-1 (6.3 days). The regression equation and correlation matrix indicated a strong relationship between growth, flowering and GA3 concentrations up to 100 mg L-1. The PCA analysis revealed that the calla lily crop is positively affected by spray timing and GA3 treatments. In the context of vegetative, reproductive, and longevity parameters of the crop, a dual spray of 100 mg L-1 GA3 can be recommended to small scale farmers and commercial growers as an alternative technique for promoting growth, yield and improving the ornamental value for commercial level production.

2.
Trials ; 22(1): 428, 2021 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-34225765

RESUMEN

BACKGROUND: Sodium valproate (VPA) has been associated with a reduced risk of head and neck cancer development. The potential protective mechanism of action is believed to be via inhibition of histone deacetylase and subsequent epigenetic reprogramming. SAVER is a phase IIb open-label, randomised control trial of VPA as a chemopreventive agent in patients with high-risk oral epithelial dysplasia (OED). The aim of the trial is to gather preliminary evidence of the clinical and biological effects of VPA upon OED and assess the feasibility and acceptability of such a trial, with a view to inform a future definitive phase III study. METHODS: One hundred and ten patients with high-risk OED will be recruited from up to 10 secondary care sites in the UK and randomised into either VPA or observation only for 4 months. Women of childbearing potential will be excluded due to the teratogenic properties of VPA. Tissue and blood samples will be collected prior to randomisation and on the last day of the intervention/observation-only period (end of 4 months). Clinical measurement and additional safety bloods will be taken at multiple time points during the trial. The primary outcome will be a composite, surrogate endpoint of change in lesion size, change in grade of dysplasia and change in LOH profile at 8 key microsatellite regions. Feasibility outcomes will include recruitment targets, compliance with the study protocol and adverse effects. A qualitative sub-study will explore patient experience and perception of the trial. DISCUSSION: The current management options for patients with high-risk OED are limited and mostly include surgical resection and clinical surveillance. However, there remains little evidence whether surgery can effectively lead to a notable reduction in the risk of oral cancer development. Similarly, surveillance is associated with concerns regarding delayed diagnosis of OED progressing to malignancy. The SAVER trial provides an opportunity to investigate the effects of a repurposed, inexpensive and well-tolerated medication as a potential chemopreventive strategy for patients with high-risk OED. The clinical and biological findings of SAVER will inform the appropriateness, design and feasibility of a definitive phase III trial. TRIAL REGISTRATION: The trial is registered with the European Clinical Trials Database ( Eudra-CT 2018-000197-30 ). ( http://www.isrctn.com/ISRCTN12448611 ). The trial was prospectively registered on 24/04/2018.


Asunto(s)
COVID-19 , Ácido Valproico , Ensayos Clínicos Fase II como Asunto , Epigénesis Genética , Femenino , Humanos , Ensayos Clínicos Controlados Aleatorios como Asunto , SARS-CoV-2 , Resultado del Tratamiento , Ácido Valproico/efectos adversos
3.
Artículo en Inglés | MEDLINE | ID: mdl-32509321

RESUMEN

BACKGROUND: Complications after major surgery are a significant cause of morbidity and mortality. Neck dissection is one of the most commonly performed major operations in Head and Neck Surgical Oncology. Significant surgical complications occur in approximately 10-20% of all patients, increasing to 40% in patients who have had previous treatment to the area or have multiple co-morbidities and/or polypharmacy.Current evidence suggests that fibrin sealants (FS) may have potential clinical advantages in Head and Neck Surgery through the reduction of complications, volume of wound drainage and retention time of the drains. However, a paucity of high-quality trial-based evidence means that a surgical trial to determine the effectiveness of FS in reducing the rate and severity of complications in patients undergoing lateral neck dissection is warranted. The DEFeND randomised external pilot trial will address critical questions on how well key components of the proposed study design work together as well as the feasibility of a future phase III trial. METHODS: The study design that is being piloted is that of a two-arm, parallel group, superiority trial with block randomisation in a 1:1 allocation ratio. The interventional arm will constitute the application of FS (Artiss, Baxter Healthcare Ltd.) to the surgical wound following completion of a neck dissection procedure, in addition to standard of care (SOC). The control arm will constitute SOC alone. Eligible patients will include patients who require a lateral neck dissection with a minimum of three cervical nodal levels. Patients who require bilateral neck procedures or undergoing immediate reconstruction with free or regional flaps will be excluded. The outcomes being assessed will be recruitment rate, screened to randomisation rate, fidelity of blinding process using blinding indices, number of missing or incomplete data entries, number of protocol deviations and number of losses to follow-up. Suitability of the outcome measures proposed for the future phase III trial will also be assessed. DISCUSSION: The anticipated challenges for this study will be recruitment, complexity of the intervention and adherence to the protocol. The outcomes will inform the design, feasibility and conduct of a future phase III surgical trial. TRIAL REGISTRATION: First participant randomised: November 06, 2018; UKCRN Portfolio ID: 37896; ISRCTN99181100.

4.
Trials ; 19(1): 22, 2018 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-29316962

RESUMEN

BACKGROUND: Osteoradionecrosis of the mandible is the most common serious complication of radiotherapy for head and neck malignancy. For decades, hyperbaric oxygen has been employed in efforts to prevent those cases of osteoradionecrosis that are precipitated by dental extractions or implant placement. The evidence for using hyperbaric oxygen remains poor and current clinical practice varies greatly. We describe a protocol for a clinical trial to assess the benefit of hyperbaric oxygen in the prevention of osteoradionecrosis during surgery on the irradiated mandible. METHODS/DESIGN: The HOPON trial is a phase III, randomised controlled, multi-centre trial. It employs an unblinded trial design, but the assessment of the primary endpoint, i.e. the diagnosis of osteoradionecrosis, is assessed on anonymised clinical photographs and radiographs by a blinded expert panel. Eligibility is through the need for a high-risk dental procedure in the mandible where at least 50-Gy radiotherapy has been received. Patients are randomised 1:1 to hyperbaric oxygen arm (Marx protocol) : control arm, but both groups receive antibiotics and chlorhexidine mouthwash. The primary endpoint is the presence of osteoradionecrosis at 6 months following surgery, but secondary endpoints include other time points, acute symptoms and pain, quality of life, and where implants are placed, their successful retention. DISCUSSION: The protocol presented has evolved through feasibility stages and through analysis of interim data. The classification of osteoradionecrosis has undergone technical refinement to ensure that robust definitions are employed. The HOPON trial is the only multi-centre RCT conducted in this clinical setting despite decades of use of hyperbaric oxygen for the prevention of osteoradionecrosis. TRIAL REGISTRATION: European Clinical Trials Database, ID: EudraCT200700622527 . First registered on 5 November 2007.


Asunto(s)
Oxigenoterapia Hiperbárica , Mandíbula/efectos de la radiación , Osteorradionecrosis/prevención & control , Ensayos Clínicos Fase III como Asunto , Humanos , Oxigenoterapia Hiperbárica/efectos adversos , Estudios Multicéntricos como Asunto , Evaluación de Resultado en la Atención de Salud , Ensayos Clínicos Controlados Aleatorios como Asunto , Tamaño de la Muestra , Investigación Biomédica Traslacional
5.
Int J Oncol ; 50(3): 768-772, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-28098864

RESUMEN

There is no standard of care in the UK or Ireland for second-line chemotherapy for patients with advanced transitional cell carcinoma (TCCU). Vinflunine is approved for TCCU patients who have failed a platinum-based regimen, and is standard of care in Europe but is not routinely available in the UK. Data were collected retrospectively on patients who received vinfluine as a second-line treatment. The aims were to document the toxicity and efficacy in a real life setting. Data were collected on 49 patients from 9 sites across the UK and Ireland [median age, 64 (IQR, 57-70) years, 33 males]. All patients had advanced metastatic TCCU. Thirteen patients had bone or liver metastases, 4 patients had PS 2 and 11 patients had HB <10. Median vinflunine administration was 3.5 cycles (range 1-18). Most common grade 3-4 toxicities were constipation (4 patients) and fatigue (3 patients). Partial response rate was 29% (14 PR, 11 SD, 19 PD, 4 NE, 1 not available). Median OS was 9.1 (6.0, 12.7) months. Results are consistent with real life data from Europe. Toxicity is further reduced with prophylactic laxative and oral antibiotics. Vinflunine is an efficient and tolerable second line treatment in advanced TCCU.


Asunto(s)
Antineoplásicos Fitogénicos/uso terapéutico , Carcinoma de Células Transicionales/tratamiento farmacológico , Neoplasias de la Vejiga Urinaria/tratamiento farmacológico , Vinblastina/análogos & derivados , Anciano , Neoplasias Óseas/secundario , Carcinoma de Células Transicionales/patología , Supervivencia sin Enfermedad , Femenino , Humanos , Irlanda , Neoplasias Hepáticas/secundario , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Resultado del Tratamiento , Reino Unido , Neoplasias de la Vejiga Urinaria/patología , Urotelio/patología , Vinblastina/uso terapéutico
6.
Inflammopharmacology ; 23(1): 65-70, 2015 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-25490949

RESUMEN

The present work investigates the anti-inflammatory, analgesic and antipyretic activity of methanolic extract of mulberry leaves of variety S-1, S-13 and S-146. The S-146 extract was further evaluated for its efficacy against adjuvant arthritis in albino rats followed by inhibitory potential for COX 1, COX 2 and 5 LOX. The HPLC analysis enumerated the presence of morin, reversterol, scopoletin and 7-hydroxy coumarin as the major constituents. The anti-inflammatory, antipyretic and analgesic activity observed in the present experiment could be accredited to the dual inhibition in the AA pathway. The inhibition of COX and LOX enzymes could be imparted to the presence of resveraterol, morin, scopoletin and 7-hydroxy coumarin.


Asunto(s)
Ácido Araquidónico/antagonistas & inhibidores , Morus , Extractos Vegetales/farmacología , Hojas de la Planta , Transducción de Señal/efectos de los fármacos , Animales , Ácido Araquidónico/metabolismo , Femenino , Masculino , Ratones , Extractos Vegetales/aislamiento & purificación , Ratas , Ratas Wistar , Transducción de Señal/fisiología
7.
Pancreatology ; 11(6): 535-45, 2011.
Artículo en Inglés | MEDLINE | ID: mdl-22094930

RESUMEN

OBJECTIVES: Pancreatic resection for cancer may produce pancreatic exocrine insufficiency (PEI), which is poorly understood. This study examined the coefficient of fat absorption (CFA), symptoms, quality of life (QoL) and the accuracy of faecal elastase-1 (FE-1) measurement to predict PEI. METHODS: Forty patients were analysed following resection for pancreatic malignancy. The primary endpoint was PEI diagnosis defined by CFA <93%; secondary endpoints were PEI diagnosis using FE-1 <200 µg/g, body mass index (BMI), and symptom and QoL analysis. Interventions were 3-day stool collection, EORTC QLQ-C30 (version 1) questionnaire and patient's diary, at 6 weeks and 3, 6 and 12 months after surgery. RESULTS: CFA <93% was present in 67% of patients at 6 weeks and in 55% at 12 months. PEI using FE-1 was present in 77 and 83% of patients, respectively. No significant changes between time-points were observed. Sensitivity, specificity, PPV, NPV and accuracy for FE-1 in detecting CFA <93% were 91, 35, 70, 71 and 70%, respectively. CFA and FE-1 levels were uncorrelated. Overall, QoL increased at 6 (p = 0.0212) and 12 (p < 0.0001) months after surgery, mainly driven by physical, role and social functioning, and by appetite. Importantly, however, BMI and symptoms were unaffected by PEI, which suggests a subclinical presentation; such patients had attributes indicating poorer QoL (notably insomnia, p = 0.0012). CONCLUSIONS: PEI was common and sustained following resection and not associated with significant symptoms. These patients had a tendency toward poorer QoL. FE-1 is a poor surrogate for diagnosing impaired fat absorption. Postoperative pancreatic enzyme replacement should be considered more routinely. and IAP.


Asunto(s)
Insuficiencia Pancreática Exocrina/etiología , Pancreatectomía/efectos adversos , Neoplasias Pancreáticas/cirugía , Calidad de Vida , Actividades Cotidianas , Anciano , Insuficiencia Pancreática Exocrina/diagnóstico , Insuficiencia Pancreática Exocrina/metabolismo , Grasas/análisis , Grasas/metabolismo , Heces/química , Heces/enzimología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Elastasa Pancreática/metabolismo , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/psicología , Valor Predictivo de las Pruebas , Estudios Prospectivos , Reproducibilidad de los Resultados , Encuestas y Cuestionarios
8.
J Mol Biol ; 393(3): 753-64, 2009 Oct 30.
Artículo en Inglés | MEDLINE | ID: mdl-19712681

RESUMEN

Positively charged counterions drive RNA molecules into compact configurations that lead to their biologically active structures. To understand how the valence and size of the cations influences the collapse transition in RNA, small-angle X-ray scattering was used to follow the decrease in the radius of gyration (R(g)) of the Azoarcus and Tetrahymena ribozymes in different cations. Small, multivalent cations induced the collapse of both ribozymes more efficiently than did monovalent ions. Thus, the cooperativity of the collapse transition depends on the counterion charge density. Singular value decomposition of the scattering curves showed that folding of the smaller and more thermostable Azoarcus ribozyme is well described by two components, whereas collapse of the larger Tetrahymena ribozyme involves at least one intermediate. The ion-dependent persistence length, extracted from the distance distribution of the scattering vectors, shows that the Azoarcus ribozyme is less flexible at the midpoint of transition in low-charge-density ions than in high-charge-density ions. We conclude that the formation of sequence-specific tertiary interactions in the Azoarcus ribozyme overlaps with neutralization of the phosphate charge, while tertiary folding of the Tetrahymena ribozyme requires additional counterions. Thus, the stability of the RNA structure determines its sensitivity to the valence and size of the counterions.


Asunto(s)
Metales/química , ARN/química , Animales , Azoarcus/química , Iones , Conformación de Ácido Nucleico , ARN Catalítico/química , Dispersión del Ángulo Pequeño , Temperatura , Tetrahymena/química , Difracción de Rayos X
9.
BMC Cancer ; 9: 66, 2009 Feb 25.
Artículo en Inglés | MEDLINE | ID: mdl-19243606

RESUMEN

BACKGROUND: Advanced pancreatic cancer has a poor prognosis, and the current standard of care (gemcitabine based chemotherapy) provides a small survival advantage. However the drawback is the accompanying systemic toxicity, which targeted treatments may overcome. This study aimed to evaluate the safety and tolerability of KAb201, an anti-carcinoembryonic antigen monoclonal antibody, labelled with I(131) in pancreatic cancer (ISRCTN 16857581). METHODS: Patients with histological/cytological proven inoperable adenocarcinoma of the head of pancreas were randomised to receive KAb 201 via either the intra-arterial or intravenous delivery route. The dose limiting toxicities within each group were determined. Patients were assessed for safety and efficacy and followed up until death. RESULTS: Between February 2003 and July 2005, 25 patients were enrolled. Nineteen patients were randomised, 9 to the intravenous and 10 to the intra-arterial arms. In the intra-arterial arm, dose limiting toxicity was seen in 2/6 (33%) patients at 50 mCi whereas in the intravenous arm, dose limiting toxicity was noted in 1/6 patients at 50 mCi, but did not occur at 75 mCi (0/3).The overall response rate was 6% (1/18). Median overall survival was 5.2 months (95% confidence interval = 3.3 to 9 months), with no significant difference between the intravenous and intra-arterial arms (log rank test p = 0.79). One patient was still alive at the time of this analysis. CONCLUSION: Dose limiting toxicity for KAb201 with I(131) by the intra-arterial route was 50 mCi, while dose limiting toxicity was not reached in the intravenous arm.


Asunto(s)
Adenocarcinoma/diagnóstico por imagen , Antígeno Carcinoembrionario/administración & dosificación , Inmunotoxinas/administración & dosificación , Radioisótopos de Yodo/administración & dosificación , Neoplasias Pancreáticas/radioterapia , Radioinmunoterapia/métodos , Adenocarcinoma/inmunología , Anciano , Anticuerpos Monoclonales/administración & dosificación , Anticuerpos Monoclonales/efectos adversos , Anticuerpos Monoclonales/inmunología , Anticuerpos Monoclonales/farmacocinética , Anticuerpos Antineoplásicos/biosíntesis , Anticuerpos Antineoplásicos/inmunología , Antígeno Carcinoembrionario/efectos adversos , Antígeno Carcinoembrionario/inmunología , Humanos , Inmunotoxinas/efectos adversos , Inmunotoxinas/inmunología , Inmunotoxinas/farmacocinética , Infusiones Intraarteriales , Infusiones Intravenosas , Radioisótopos de Yodo/efectos adversos , Radioisótopos de Yodo/farmacocinética , Persona de Mediana Edad , Neoplasias Pancreáticas/inmunología , Radiografía , Radioinmunoterapia/efectos adversos , Tasa de Supervivencia
10.
J Mol Biol ; 386(4): 1167-78, 2009 Mar 06.
Artículo en Inglés | MEDLINE | ID: mdl-19154736

RESUMEN

Stable RNAs must fold into specific three-dimensional structures to be biologically active, yet many RNAs form metastable structures that compete with the native state. Our previous time-resolved footprinting experiments showed that Azoarcus group I ribozyme forms its tertiary structure rapidly (tau < 30 ms) without becoming significantly trapped in kinetic intermediates. Here, we use stopped-flow fluorescence spectroscopy to probe the global folding kinetics of a ribozyme containing 2-aminopurine in the loop of P9. The modified ribozyme was catalytically active and exhibited two equilibrium folding transitions centered at 0.3 and 1.6 mM Mg2+, consistent with previous results. Stopped-flow fluorescence revealed four kinetic folding transitions with observed rate constants of 100, 34, 1, and 0.1 s-1 at 37 degrees C. From comparison with time-resolved Fe(II)-ethylenediaminetetraacetic acid footprinting of the modified ribozyme under the same conditions, these folding transitions were assigned to formation of the IC intermediate, tertiary folding and docking of the nicked P9 tetraloop, reorganization of the P3 pseudoknot, and refolding of nonnative conformers, respectively. The footprinting results show that 50-60% of the modified ribozyme folds in less than 30 ms, while the rest of the RNA population undergoes slow structural rearrangements that control the global folding rate. The results show how small perturbations to the structure of the RNA, such as a nick in P9, populate kinetic folding intermediates that are not observed in the natural ribozyme.


Asunto(s)
Azoarcus/enzimología , Conformación de Ácido Nucleico , ARN Catalítico/química , 2-Aminopurina/metabolismo , Secuencia de Bases , Fluorescencia , Colorantes Fluorescentes , Peróxido de Hidrógeno , Hierro , Cinética , Magnesio/farmacología , Modelos Biológicos , Datos de Secuencia Molecular , Mutación/genética , Conformación de Ácido Nucleico/efectos de los fármacos , ARN Catalítico/genética , Temperatura , Factores de Tiempo
11.
Biochem Biophys Res Commun ; 377(1): 262-7, 2008 Dec 05.
Artículo en Inglés | MEDLINE | ID: mdl-18845125

RESUMEN

The high mobility group protein HMGB1 is a highly abundant chromosomal protein known to interact preferentially with DNA that is branched, bent or otherwise structurally altered. Biologically the protein is thought to facilitate promoter attachment by transcription factors. Recently, however, HMGB1 has been shown to have biological roles beyond that of an architectural DNA-binding protein. Here we investigate the binding interactions of recombinant HMGB1 proteins with two branched RNA's E. coli 5S rRNA and the group I intron ribozyme from Azoarcus pre-tRNA(Ile). Using competitive electrophoretic mobility and circular dichroism binding assays, we show that HMGB proteins bind both substrates with high affinity. We also report that a recombinant rat HMGB protein, rHMGB1b, inhibits RNA cleavage by the ribozyme. These results raise the possibility that HMGB proteins possess structure dependent RNA binding activity and can modulate RNA processing as well as transcription.


Asunto(s)
Proteína HMGB1/química , ARN Bacteriano/metabolismo , ARN Catalítico/química , ARN Ribosómico 5S/química , Azoarcus/enzimología , Unión Competitiva , Dicroismo Circular , Ensayo de Cambio de Movilidad Electroforética , Escherichia coli , Proteína HMGB1/genética , Proteína HMGB1/metabolismo , Unión Proteica , ARN Catalítico/metabolismo , ARN Ribosómico 5S/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
12.
J Am Chem Soc ; 130(4): 1296-303, 2008 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-18179212

RESUMEN

RNAs must fold into unique three-dimensional structures to function in the cell, but how each polynucleotide finds its native structure is not understood. To investigate whether the stability of the tertiary structure determines the speed and accuracy of RNA folding, docking of a tetraloop with its receptor in a bacterial group I ribozyme was perturbed by site-directed mutagenesis. Disruption of the tetraloop or its receptor destabilizes tertiary interactions throughout the ribozyme by 2-3 kcal/mol, demonstrating that tertiary interactions form cooperatively in the transition from a native-like intermediate to the native state. Nondenaturing PAGE and RNase T1 digestion showed that base pairs form less homogeneously in the mutant RNAs during the transition from the unfolded state to the intermediate. Thus, tertiary interactions between helices bias the ensemble of secondary structures toward native-like conformations. Time-resolved hydroxyl radical footprinting showed that the wild-type ribozyme folds completely within 5-20 ms. By contrast, only 40-60% of a tetraloop mutant ribozyme folds in 30-40 ms, with the remainder folding in 30-200 s via nonnative intermediates. Therefore, destabilization of tetraloop-receptor docking introduces an alternate folding pathway in the otherwise smooth energy landscape of the wild-type ribozyme. Our results show that stable tertiary structure increases the flux through folding pathways that lead directly and rapidly to the native structure.


Asunto(s)
ARN/química , Azoarcus/metabolismo , Electroforesis en Gel de Poliacrilamida , Radical Hidroxilo , Modelos Químicos , Mutagénesis Sitio-Dirigida , Mutación , Conformación de Ácido Nucleico , Desnaturalización de Ácido Nucleico , Nucleótidos/química , ARN Catalítico/química , Ribonucleasa P/química , Ribonucleasa T1/química , Ribonucleasas/química , Termodinámica
13.
J Mol Biol ; 353(5): 1199-209, 2005 Nov 11.
Artículo en Inglés | MEDLINE | ID: mdl-16214167

RESUMEN

Large RNAs collapse into compact intermediates in the presence of counterions before folding to the native state. We previously found that collapse of a bacterial group I ribozyme correlates with the formation of helices within the ribozyme core, but occurs at Mg2+ concentrations too low to support stable tertiary structure and catalytic activity. Here, using small-angle X-ray scattering, we show that Mg2+-induced collapse is a cooperative folding transition that can be fit by a two-state model. The Mg2+ dependence of collapse is similar to the Mg2+ dependence of helix assembly measured by partial ribonuclease T1 digestion and of an unfolding transition measured by UV hypochromicity. The correspondence between multiple probes of RNA structure further supports a two-state model. A mutation that disrupts tertiary contacts between the L9 tetraloop and its helical receptor destabilized the compact state by 0.8 kcal/mol, while mutations in the central triplex were less destabilizing. These results show that native tertiary interactions stabilize the compact folding intermediates under conditions in which the RNA backbone remains accessible to solvent.


Asunto(s)
ARN Catalítico/química , ARN/química , Azoarcus/química , Proteínas Bacterianas/química , Estabilidad de Enzimas , Magnesio , Modelos Moleculares , Mutación , Conformación de Ácido Nucleico , Desnaturalización de Ácido Nucleico , ARN Catalítico/genética , Difracción de Rayos X
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