RESUMO
Objective: To explore the related factors of high-volume lymph node metastasis (HVM) in multifocality papillary thyroid carcinoma (MPTC). Methods: The clinical and pathological data of multifocality papillary thyroid carcinoma (MPTMC, d≤10 mm) and MPTC (d>10 mm) collected from Hangzhou First People's Hospital from January 2010 to March 2023 were retrospectively analyzed. Univariate and multivariate logistic regression analysis were used to analyze the relevant factors of HVM. Results: Among 566 cases of MPTMC and 381 cases of MPTC, there were 72 males and 494 females in MPTMC, 106 males and 275 females in MPTC, respectively. The median age of the patients was 47 (39, 54) and 47 (34, 56) years, respectively, and the incidence of HVM was 4.6% (26/566) and 21.5% (82/381), respectively (χ2=64.588, P<0.001). Univariate analysis showed that in patients with MPTMC and MPTC, the incidence of HVM in males was higher than that in females [15.3% (11/72) vs 3.0% (15/494) (χ2=21.487, P<0.001) in MPTMC, 33.2% (35/106) vs 17.1% (47/275) (χ2=11.492, P=0.001) in MPTC]. The age of the HVM group was lower than that of the non-HVM group [41 (33, 50) vs 48 (39, 54) years (Z=-2.128, P=0.033) in MPTMC, 38 (29, 48) vs 48 (36, 57) years (Z=-4.987, P<0.001) in MPTC]. The maximum diameter of tumors in the HVM group were higher than those in the non-HVM group [7.0 (5.0, 10.0) mm vs 6.0 (5.0, 8.0) mm (Z=-2.558, P=0.011) in MPTMC, 17.5 (13.0, 25.0) mm vs 15.0 (12.0, 20.0) mm (Z=-2.871, P=0.004) in MPTC]. Multivariate logistic regression analysis showed that larger tumor size (OR=3.027, 2.378; 95%CI: 1.287-7.117, 1.404-4.030; P=0.011, 0.001), male (OR=5.398, 1.909; 95%CI: 2.284-12.758, 1.113-3.274; P<0.001, P=0.019), and younger age (OR=3.889, 3.136; 95%CI: 1.686-8.969, 1.837-5.355; P=0.001, P<0.001) were all risk factors for the occurrence of HVM in MPTMC and MPTC. Conclusion: The proportion of HVM in MPTC patients was higher than that in MPTMC, and larger maximum diameter, male gender and younger age are related factors for HVM in MPTMC and MPTC.
Assuntos
Carcinoma Papilar , Neoplasias da Glândula Tireoide , Feminino , Humanos , Masculino , Câncer Papilífero da Tireoide , Estudos Retrospectivos , Metástase Linfática/patologia , Fatores de Risco , LinfonodosRESUMO
AIM: To investigate the efficacy of the maximum signal intensity of tumour on T1-weighted magnetic resonance imaging (MRI) images for differentiating Warthin's tumours (WTs) from pleomorphic adenomas (PAs) and malignant tumours (MTs). MATERIALS AND METHODS: One hundred and fifty-four histopathologically confirmed parotid tumours, including 76 PAs, 45 WTs, and 33 MTs, were analysed. MRI results were compared with pathological findings. The maximum signal intensity of tumour and the average signal intensity of spinal cord were measured on T1-weighted images, then the tumour-to-spinal cord signal intensity ratio (T1-max-SIR) was calculated. The distribution of T1-max-SIRs among the three groups of tumours was analysed using the Mann-Whitney U-test. Receiver operating characteristic curves were generated to assess the ability of T1-max-SIRs to differentiate parotid tumours. In addition, the interobserver agreement between readers was assessed using interclass correlation coefficient (ICC). RESULTS: T1-max-SIRs were higher in WTs than in PAs (p<0.001) and MTs (p<0.001), and no significant difference was found between PAs and MTs (p=0.151). The area under the curve (AUC) of T1-max-SIRs for differentiating WTs from PAs was 0.901, with a sensitivity of 91.1% and a specificity of 82.9%. The AUC of T1-max-SIRs for differentiating WTs from MTs was 0.851, with a sensitivity of 88.9% and a specificity of 78.8%. Readers had excellent interobserver agreement on T1-max-SIRs (ICC = 0.989; 95% confidence interval, 0.985-0.992). CONCLUSIONS: T1-max-SIRs can be useful for differentiating WTs from PAs and MTs with high diagnostic efficiency.
Assuntos
Adenolinfoma/diagnóstico por imagem , Adenolinfoma/patologia , Adenoma Pleomorfo/diagnóstico por imagem , Adenoma Pleomorfo/patologia , Imageamento por Ressonância Magnética/métodos , Neoplasias Parotídeas/diagnóstico por imagem , Neoplasias Parotídeas/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Glândula Parótida/diagnóstico por imagem , Glândula Parótida/patologia , Estudos RetrospectivosRESUMO
To generate an efficient tool used in Xenopus oocyte expression for in situ investigation of channel receptor expression, distribution and function, the C-terminus of the honeybee (Apis mellifera L.) resistant to dieldrin (RDL) subunit was fused with *FP, including monomeric red, enhanced yellow or enhanced green fluorescent protein (referred to as mRFP, EYFP and EGFP, respectively). In the present study, all fused *FP-AmRDLs could be visualized using fluorescence and laser confocal microscopy in cRNA-injected oocytes. Fluorescence was distributed isotropically in the cellular membrane. The potencies of the agonist γ-aminobutyric acid (GABA), but not ß-alanine, and the test antagonists (fipronil, flufiprole, dieldrin, α-endosulfan, bifenazate and avermectin B1a) in the *FP-AmRDL receptor did not significantly differ from that of the untagged receptor with two-electrode voltage clamp detection. The half maximal effective concentrations (EC50 s) of GABA in AmRDL, EGFP-AmRDL, EYFP-AmRDL and mRFP-AmRDL receptors were 11.98, 12.61, 18.92 and 22.11 µM, respectively, and those of ß-alanine were 651.6, 629.6, 1643.0 and 2146.0 µM, respectively. Inhibition percentages of test antagonists against *FP-AmRDL and AmRDL were not significantly different from each other. Overall, the consistency in functional properties between *FP-AmRDL and AmRDL receptors makes pGH19-*FP a promising tool for further in situ investigation of GABA receptors.
Assuntos
Abelhas/genética , Conjugação Genética/genética , Proteínas de Insetos/genética , Resistência a Inseticidas/genética , Proteínas Luminescentes/genética , Receptores de GABA-A/genética , Animais , Abelhas/efeitos dos fármacos , Proteínas de Fluorescência Verde/genética , Proteínas de Insetos/metabolismo , Inseticidas/farmacologia , Oócitos , Receptores de GABA-A/metabolismo , Xenopus/genética , Proteína Vermelha FluorescenteRESUMO
Objective: To establish the ischemia reperfusion injury model in rat after lung transplantation(LT) and explore the expression of high mobility group box 1 protein(HMGB1) after intravenous injection with bone marrow mesenchymal stem cells(MSCs). Methods: Forty healthy 8-10 weeks male SD rats were randomly divided into four groups including the sham-operated group, ischemia-reperfusion (IR), Saline-IR and MSC-IR group. The sham-operated rats were only conducted thoracotomy without lung transplantation and the rest groups were respectively conducted with the left LT, left LT followed by 1 ml saline and left LT followed by 1 ml MSCs (1.0×10(7)/ml). Four groups of rats were killed at 24 h after reperfusion. The blood and left lung tissue were collected. Oxygenation index(OI) and the ratio of wet/dry in four groups were detected and histological sections stained with hematoxylin and eosin (HE) were made. HMGB1 levels in serum were detected with ELISA. Real-time PCR and Western blot were performed to detect the expression of HMGB1 in mRNA and protein levels. Results: The OI in four groups were respectively 383±15, 174±24, 170±30 and 217±21.OI in IR and Saline-IR group decreased compared with the sham-operated group , all P<0.01. The OI increased after injection with MSCs compared with IR group, P<0.01. The histological images showed the marked inflammatory infiltrates and interalveolar septal thickening in IR group. Treatment with MSCs reduced inflammatory injury.The ratio of wet/dry in IR group and Saline-IR group increased compared with the sham-operated group((5.38±0.19), (5.24±0.15) vs (4.16±0.12), all P<0.05). Ratio in MSC-IR group decreased compared with the IR group (4.47±0.14) vs (5.38±0.19), P<0.05. ELISA results showed that HMGB1 level increased significantly in IR group (287±37)ng/ml, Saline-IR group (260±24)ng/ml and MSC-IR group (101±14)ng/ml when compared with the sham-operated group (41±5) ng/ml. The serum HMGB1 level in IR group was positively correlated with the OI (r=0.759, P<0.05) and wet/dry ratio (r=0.725, P<0.05). RT-PCR showed that HMGB1 mRNA level in sham-operated group was the lowest and increased significantly in IR group, while decreased significantly in MSC-IR group compared with IR group and Saline-IR group(P<0.01). The results of HMGB1 expression at protein level by Western blot were consistent with the mRNA level. Conclusion: Lung transplantation can induce the expression of HMGB1 but HMGB1 level of lung tissue decreased significantly after the treatment with MSCs, which indicated that MSCs might play an important role in protecting transplanted lung via HMGB1.
Assuntos
Células-Tronco Mesenquimais , Animais , Proteína HMGB1 , Transplante de Pulmão , Masculino , Ratos , Ratos Sprague-Dawley , Traumatismo por ReperfusãoRESUMO
Objective: To explore the risk factors of primary graft dysfunction (PGD) after lung transplantation and provide a new therapeutic strategy for PGD. Methods: A retrospective analysis of lung transplant patients from January 2014 to July 2017 in Henan Provincial People's Hospital.According to the PGD classification standard established by the International Society for Heart and Lung Transplantation, the association of potential risk factors with PGD was analyzed by using multivariable Logistic regression. Results: Fourteen of 30 patients (46.7%) developed grade 3 PGD.There was no significantly statistical difference in gender, etiology, duration of anesthesia, amount of blood transfusion, amount of blood transfusion and donor gender(all P>0.05). Body mass index (BMI), donor pulmonary cold ischemia time, duration of operation, extracorporeal membrane lung oxygenator (ECMO), systolic pulmonary arterial pressure and donor smoking history were all higher than those of non-PGD patients (all P<0.05). Independent risk factors for PGD were donor pulmonary cold ischemia time (OR 1.032, 95%CI 1.000-1.065, P=0.048); systolic pulmonary arterial pressure (OR 1.258, 95%CI 0.969-1.632, P=0.007); donor smoking (OR 8.879, 95%CI 1.096-71.913, P=0.041). Conclusion: Donor pulmonary ischemic time, systolic pulmonary arterial pressure and donor smoking history are PGD risk factors, which provide new ideas for PGD treatment.
Assuntos
Disfunção Primária do Enxerto , Humanos , Modelos Logísticos , Transplante de Pulmão , Estudos Retrospectivos , Medição de Risco , Fatores de RiscoRESUMO
The ryanodine receptor (RyR) of the calcium release channel is the main target of anthranilic and phthalic diamide insecticides which have high selective insecticidal activity relative to mammalian toxicity. In this study, the full-length cDNA of Chilo suppressalis RyR (CsRyR) was isolated and characterized. The CsRyR mRNA has an open reading frame (ORF) of 15,387bp nucleotides, which encodes 5128 amino acids with GenBank ID: KR088972. Comparison of protein sequences showed that CsRyR shared high identities with other insects of 77-96% and lower identity to mammals and nematodes with only 42-45%. One alternative splicing site (KENLG) unique to Lepidoptera was found and two exclusive exons of CsRyR (I /II) were revealed. Spatial and temporal expression of CsRyR mRNA was at the highest relative level in 3rd instar larvae and head (including brain and muscle), and at the lowest expression level in egg and fat body. The expression levels of whole body CsRyR mRNA were increased remarkably after injection of 4th instar larvae with chlorantraniliprole at 0.004 to 0.4µg/g. This structural and functional information on CsRyR provides the basis for further understanding the selective action of chlorantraniliprole and possibly other diamide insecticides.
Assuntos
Proteínas de Insetos/genética , Inseticidas/toxicidade , Larva/genética , Lepidópteros/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , ortoaminobenzoatos/toxicidade , Processamento Alternativo , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , DNA Complementar/genética , Perfilação da Expressão Gênica , Larva/efeitos dos fármacos , Lepidópteros/efeitos dos fármacos , Filogenia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Análise de Sequência de DNARESUMO
Objective: To evaluate the value of CT in the risk assessment of thyroid benign nodules (BN) and malignant nodules (MN). Methods: The CT signs of 461 pieces of MN in 447 cases and 548 pieces of BN in 484 cases were retrospectively analyzed, the diagnoses were confirmed by histology, including nodular morphology, cookie bite sign, microcalcification, enhanced range narrow/blurred, cystic changes and enhanced.The signs of CT were analyzed by univariate and multivariate regression analysis.The positive CT signs were calculated to assess sensitivity and specificity in the diagnosis of BN and MN. Results: Univariate and multivariate analysis showed that irregular nodular morphology (χ(2)=509.263, P<0.001, OR=5.297), cookie bite sign (χ(2)=504.619, P<0.001, OR=3.467), microcalcification (χ(2)=97.793, P<0.001, OR=1.730), enhanced range reduction/blur (χ(2)=361.967, P<0.001, OR=5.729) were more common in MN.Cysts changes (χ(2)=223.208, P<0.001, OR=7.537) and enhancement signs (χ(2)=65.983, P<0.001, OR=10.782) were more common in BN.The sensitivity and specificity of irregular nodular morphology in the diagnosis of MN were 80.5% and 90%, those in cookie bite sign were 74.2% and 94.3%, microcalcification were 35.6% and 90.1%, enhanced range reduction/blur were 80.7% and 79.4%.The sensitivity and specificity of capsule-based and high-enhanced BN diagnosis were 42.2% and 98.1%, 19.0% and 97.4%, respectively. Conclusions: Irregular shape, cookie bite sign, microcalcification and enhanced range of narrowing/blur are significant CT signs in the assessment of MN, and cystic changes and enhancement are significant CT signs in the evaluation of BN.The diagnostic efficiency of various CT signs varies greatly, and combination of multiple CT signs can improve the diagnostic efficiency.
Assuntos
Nódulo da Glândula Tireoide , Diagnóstico Diferencial , Humanos , Estudos Retrospectivos , Neoplasias da Glândula Tireoide , Tomografia Computadorizada por Raios XRESUMO
Mankind faces several global challenges such as chronic and acute hunger, global poverty, energy deficiency and environment conservation. Common biotechnologies based on batch, fluidbed and other similar processes are now extensively used for the production of a wide range of products such as antibiotics, biofuels, cultured and fermented food products. Unfortunately, these processes suffer from low efficiency, high energy demand, low controllability and rapid biocatalyst degradation by microbiological attack, and thus still are not capable of seriously addressing the global hunger and energy deficiency challenges. Moreover, sustainable future technologies require minimizing the environmental impact of toxic by-products by implementing the "life produces organic matter, organic matter sustains life" principle. Nanostructure-based biotechnology is one of the most promising approaches that can help to solve these challenges. In this work we briefly review the unique features of the carbon-based nanostructured platforms, with some attention paid to other nanomaterials. We discuss the main building blocks and processes to design and fabricate novel platforms, with a focus on dense arrays of the vertically-aligned nanostructures, mainly carbon nanotubes and graphene. Advantages and disadvantages of these systems are considered.
Assuntos
Reatores Biológicos , Biotecnologia , Nanotubos de Carbono , NanoestruturasRESUMO
Structural defects inevitably appear during the nucleation event that determines the structure and properties of single-walled carbon nanotubes. By combining ion bombardment experiments with atomistic simulations we reveal that ion bombardment in a suitable energy range allows these defects to be healed resulting in an enhanced nucleation of the carbon nanotube cap. The enhanced growth of the nanotube cap is explained by a nonthermal ion-induced graphene network restructuring mechanism.
RESUMO
Acetylcholinesterase (AChE, EC 3.1.1.7) is a key enzyme in terminating synaptic transmission. We knocked down the expression of Csace1 or Csace2 using chemically synthesized small interfering RNAs (siRNAs) designed from divergent regions. The mRNA abundance of the two ace genes was reduced to 50-70% of control levels. The enzyme activities were decreased to 40-70%. Silencing of Csace1 or Csace2 resulted in a ~25% mortality rate. Knockdown of Csace1 had major effects on larval growth inhibition and resulted in reduced larval weight and length, malformation and motor disability, whereas silencing of Csace2 had only minor effects. These results suggested that both AChE-1 and AChE-2 have important roles in maintaining life in this insect and indicated that AChE-1 might have nontypical functions in regulating larval growth and motor ability.
Assuntos
Acetilcolinesterase/genética , Mariposas/genética , Atividade Motora/genética , Interferência de RNA , Acetilcolinesterase/metabolismo , Animais , Técnicas de Silenciamento de Genes , Larva/crescimento & desenvolvimento , Mariposas/crescimento & desenvolvimento , RNA Interferente PequenoRESUMO
Euphrates poplar (Populus euphratica Oliv.) has heteromorphic leaves including strip, lanceolate, ovate, and broad-ovate leaves from base to top in the mature canopy. To clarify how diameter at breast height (DBH) and tree height affect the functional characteristics of all kinds of heteromorphic leaves, we measured the morphological anatomical structure and physiological indices of five crown heteromorphic leaves of P. euphratica at 2, 4, 6, 8, 10, and 12 m from the same site. We also analysed the relationships between morphological structures and physiological characteristics of heteromorphic leaves and DBH and the height of heteromorphic leaves. The results showed that the number of abnormalities regarding blade width, leaf area, leaf thickness, leaf mass per area, cuticle layer thickness, palisade tissue thickness, and palisade tissue/sponge tissue ratio increased with size order and sampling height gradient. Net photosynthetic rate, transpiration rate, stomatal conductance, instantaneous water use efficiency, stable delta carbon isotope ratio, proline and malondialdehyde (MDA) content increased with DBH and sampling height. By contrast, blade length, leaf shape index, and intercellular CO2 concentration decreased with the increase in path order and sampling height gradient. Although MDA content and leaf sponge thickness were not correlated with DBH or sampling height, other morphological structure and physiological parameters were significantly correlated with these variables. In addition, correlations were found among leaf morphology, anatomical structure, and physiological index parameters indicating that they changed with path order and tree height gradient. The differences in the morphology, anatomic structure and physiological characteristics of the heteromorphic leaves ofP. euphratica are related to ontogenesis stage and coronal position.
Assuntos
Folhas de Planta , Populus , Fotossíntese/fisiologia , Folhas de Planta/anatomia & histologia , Folhas de Planta/fisiologia , Populus/anatomia & histologia , Populus/fisiologia , Água/metabolismoRESUMO
We report dewetting of thermodynamically stable, thick (approximately 100 nm) polystyrene films by titanium ion implantation. The dynamic dewetting patterns in time evolution are recorded. The dewetting mechanism is determined to be heterogeneous nucleation, where the defects and Ti nanoparticles formed by ion implantation serve as the nuclei. In addition, we observe abundant rims with regular polygonal shapes in dewetting patterns. This is attributed to fingering instability, which results from the balance between the driving force arisen from thermally induced surface tension gradient and the resistive forces from the combination of friction force, Laplace pressure and long-range van der Waals interactions. Finally, a model based on mass conservation is used to qualitatively describe the transition from circular to polygonal shaped rims at a critical diameter for holes.
RESUMO
Two piggyBac-like elements (PLEs) were identified in the cotton bollworm, Helicoverpa armigera, and were designated as HaPLE1 and HaPLE2. HaPLE1 is flanked by 16 bp inverted terminal repeats (ITRs) and the duplicated TTAA tetranucleotide, and contains an open reading frame (ORF) of 1794 bp with the presumed DDD domain, indicating that this element may be an active autonomously mobile element. HaPLE2 was found with the same ITRs, but lacks the majority of an ORF-encoding transposase. Thus, this element was thought to be a non-autonomous element. Transposable element displays and distribution of the two PLEs in individuals from three different H. armigera populations suggest that transmobilization of HaPLE2 by the transposase of HaPLE1 may be likely, and mobilization of HaPLE1 might occur not only within the same individual, but also among different individuals. In addition, horizontal transfer was probably involved in the evolution of PLEs between H. armigera and Trichoplusia ni.
Assuntos
Elementos de DNA Transponíveis , Lepidópteros/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Clonagem Molecular , DNA/química , DNA/genética , Lepidópteros/enzimologia , Dados de Sequência Molecular , Filogenia , Reação em Cadeia da Polimerase , Alinhamento de Sequência , Sequências Repetidas Terminais , Transposases/genéticaRESUMO
ZnO:Co nanoclusters were synthesized by nanocluster-beam deposition with averaged particle size of 5 nm and porous structure, which were for the first time adopted to construct a novel amperometric glucose biosensor. Glucose oxidase was immobilized into the ZnO:Co nanocluster-assembled thin film through Nafion-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of the ZnO:Co nanoclusters, the constructed glucose biosensor showed a high sensitivity of 13.3 microA/mA cm2. The low detection limit was estimated to be 20 microM (S/N=3) and the apparent Michaelis-Menten constant was found to be 21 mM, indicating the high affinity of the enzyme on ZnO:Co nanoclusters to glucose. The results show that the ZnO:Co nanocluster-assembled thin films with nanoporous structure and nanocrystallites have potential applications as platforms to immobilize enzyme in biosensors.
Assuntos
Técnicas Biossensoriais/instrumentação , Cobalto/química , Eletroquímica/instrumentação , Glucose/análise , Nanoestruturas/química , Óxido de Zinco/química , Técnicas Biossensoriais/métodos , Eletroquímica/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
In this paper, the regularity on spontaneous discharges of the single unit in amygdaloid nucleus (AMYG) in rabbits were analyzed and whether the signal of Electro-acupuncture (EA) at Neiguan (P 6) can reach the AMYG was further observed with the technique of glass microelectrode. It was found that the signals of EA at Neiguan can reach AMYG and activate or inhibit the electrical activity of some neurons, manifesting two response patterns: frequency-increasing and frequency-decreasing. Additionally, the same neuron had a different response to the signals of EA at Neiguan and Zusanli (St 36), suggesting that a relative specificity of acupoints is present.
Assuntos
Terapia por Acupuntura , Tonsila do Cerebelo/fisiologia , Animais , Estimulação Elétrica , Eletrofisiologia , Feminino , Masculino , Neurônios/fisiologia , CoelhosRESUMO
AIM: To explore the value of morphological classification in predicting malignant transformation in multiple exostoses (ME). PATIENTS AND METHODS: The imaging data of 116 patients (totally 190 tumors) with ME were retrospectively analyzed. All the tumors were pathology confirmed after surgical resection, including 175 exostoses from 101 patients, and 15 exostotic chondrosarcomas in 15 cases. Based on the ratio of diameter between tumor tip and tumor base (R1), tumors were classified into two types: cauliflower-like tumor (R1 ≥ 1.0) and non-cauliflower-like tumor (R1 < 1.0). In addition, non-cauliflower-like tumors were further classified into two subtypes according to the ratio of tumor height to tumor base diameter: sessile type (R2 < 1.0) and pedunculated type (R2 ≥ 1.0). The relationship between tumor shape and malignant transformation was studied. RESULTS: Of all the 175 exostoses from 101 patients, 27 were cauliflower-like tumors and 148 were non-cauliflower-like tumors. Of all the 15 exostotic chondrosarcomas in 15 cases, most tumors were cauliflower-like (c2 = 38.0075, p < 0.05). Cauliflower-like tumor for the prediction of exostotic chondrosarcoma, the sensibility, specificity, positive predictive value, negative predictive value were 86.7%, 84.6%, 32.5%, 98.7%, respectively. CONCLUSIONS: Tumor malignant transformation was more common in cauliflower-like tumors than in non-cauliflower-like tumors. The morphological classification and preventive resection of cauliflower-like tumors maybe helpful in preventing the malignant transformation of ME.
Assuntos
Transformação Celular Neoplásica/patologia , Exostose Múltipla Hereditária/patologia , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto JovemRESUMO
Controlled synthesis of both single-walled carbon nanotube and carbon nanowire networks using the same CVD reactor and Fe/Al(2)O(3) catalyst by slightly altering the hydrogenation and temperature conditions is demonstrated. Structural, bonding and electrical characterization using SEM, TEM, Raman spectroscopy, and temperature-dependent resistivity measurements suggest that the nanotubes are of a high quality and a large fraction (well above the common 33% and possibly up to 75%) of them are metallic. On the other hand, the carbon nanowires are amorphous and semiconducting and feature a controlled sp(2)/sp(3) ratio. The growth mechanism which is based on the catalyst nanoisland analysis by AFM and takes into account the hydrogenation and temperature control effects explains the observed switch-over of the nanostructure growth modes. These results are important to achieve the ultimate control of chirality, structure, and conductivity of one-dimensional all-carbon networks.
Assuntos
Acetilcolinesterase/genética , Afídeos/efeitos dos fármacos , Afídeos/enzimologia , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Acetilcolinesterase/metabolismo , Animais , Afídeos/genética , Clonagem Molecular , Regulação Enzimológica da Expressão Gênica/genética , Mutação/genéticaRESUMO
Single crystals of d(CTCCT(S)CCGCGCG).d(CGCGCGGAG) have been grown by the vapor-diffusion method using 2-methyl-2,4-pentanediol as a precipitant. The crystals are tetragonal, space group P4(2), with unit-cell parameters a = b = 53.8, c = 43.1 A, and diffract to 1.8 A resolution at a synchrotron X-ray beamline. In the crystal, the asymmetric unit contains one copy of the construct. The two halves of the structure are related by non-crystallographic twofold symmetry. These observations are consistent with the conclusion that the sequences of the 12-mer and 9-mer oligonucleotides form a duplex DNA at one end and a triplex DNA at the other end.
Assuntos
DNA/química , DNA/isolamento & purificação , Oligodesoxirribonucleotídeos/química , Oligodesoxirribonucleotídeos/isolamento & purificação , Sequência de Bases , Cristalização , Cristalografia por Raios X , Conformação de Ácido NucleicoRESUMO
Extended purine sequences on a DNA strand can lead to the formation of triplex DNA in which the third strand runs parallel to the purine strand. Triplex DNA structures have been proposed to play a role in gene expression and recombination and also have potential application as antisense inhibitors of gene expression. Triplex structures have been studied in solution by NMR, but have hitherto resisted attempts at crystallization. Here, we report a novel design of DNA sequences, which allows the first crystallographic study of DNA segment containing triplexes and its junction with a duplex. In the 1.8 A resolution structure, the sugar-phosphate backbone of the third strand is parallel to the purine-rich strand. The bases of the third strand associate with the Watson and Crick duplex via Hoogsteen-type interactions, resulting in three consecutive C(+).GC, BU.ABU (BU = 5-bromouracil), and C(+).GC triplets. The overall conformation of the DNA triplex has some similarity to the B-form, but is distinct from both A- and B-forms. There are large changes in the phosphate backbone torsion angles (particularly gamma) of the purine strand, probably due to the electrostatic interactions between the phosphate groups and the protonated cytosine. These changes narrow the minor groove width of the purine-Hoogsteen strands and may represent sequence-specific structural variations of the DNA triplex.