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Roy S Fortier JM Nagarajan R Tripathy S Kumar J Samuelson LA Bruno FF 《Biomacromolecules》2002,3(5):937-941
A new biomimetic route for the synthesis of a conducting molecular complex of polyaniline (Pani) and a natural polyelectrolyte, lignosulfonate (LGS) is presented. A poly(ethylene glycol) modified hematin (PEG-hematin) was used to catalyze the polymerization of aniline in the presence of LGS to form a Pani/LGS complex. UV-vis, FTIR, conductivity and TGA studies for the LGS-polyaniline complex indicate the presence of a thermally stable and electrically conductive form of polyaniline. Also the presence of LGS in this complex, an inexpensive byproduct from pulp processing, provides a unique combination of properties such as electronic conductivity, processability and biodegradability. The use of this conductive complex for corrosion protection is also proposed. 相似文献
84.
Structural analysis of the initial steps in protein folding is difficult because of the swiftness with which these steps occur. Hence, the link between initial polypeptide chain collapse and formation of secondary and other specific structures remains poorly understood. Here, an equilibrium model has been developed for characterizing the initial steps of folding of the small protein barstar, which lead to the formation of a productive molten globule in the folding pathway. In this model, the high-pH-unfolded form (D form) of barstar, which is shown to be as unstructured as the urea-denatured form, is transformed progressively into a molten globule B form by incremental addition of the salt Na(2)SO(4) at pH 12. At very low concentrations of Na(2)SO(4), the D form collapses into a pre-molten globule (P) form, whose volume exceeds that of the native (N) state by only 20%, and which lacks any specific structure as determined by far- and near-UV circular dichroism. At higher concentrations of Na(2)SO(4), the P form transforms into the molten globule (B) form in a highly noncooperative transition populated by an ensemble of at least two intermediates. The B form is a dry molten globule in which water is excluded from the core, and in which secondary structure develops to 65% and tertiary contacts develop to 40%, relative to that of the native protein. Kinetic refolding experiments carried out at pH 7 and at high Na(2)SO(4) concentrations, in which the rate of folding of the D form to the N state is compared to that of the B form to the N state, indicate conclusively that the B form is a productive intermediate that forms on the direct pathway of folding from the D form to the N state. 相似文献
85.
Navarro CE Saeed SA Murdock C Martinez-Fuentes AJ Arora KK Krsmanovic LZ Catt KJ 《Molecular endocrinology (Baltimore, Md.)》2003,17(12):1792-1804
Immortalized GnRH neurons (GT1-7) express receptors for estrogen [estrogen receptor-alpha and-13(ERa and ERI3)] and progesterone (progesterone receptor A) and exhibit positive immunostaining for both intracellular and plasma membrane ERs. Exposure of GT1-7 cells to picomolar estradiol concentrations for 5-60 min caused rapid, sustained,and dose-dependent inhibition of cAMP production. In contrast, treatment with nanomolar estradiol concentrations for 60 min increased cAMP production. The inhibitory and stimulatory actions of estradiol on cAMP formation were abolished by the ER antagonist, ICI 182,780. The estradiol-induced inhibition of cAMP production was prevented by treatment with pertussis toxin, consistent with coupling of the plasma membrane ER to an inhibitory G protein. Coimmunoprecipitation studies demonstrated an estradiol-regulated stimulatory interaction between ERa and G,3 that was prevented by the ER antagonist, ICI 182,780. Exposure of perifused GT1-7 cells and hypothalamic neurons to picomolar estradiol levels increased the GnRH peak interval, shortened peak duration, and increased peak amplitude. These findings indicate that occupancy of the plasma membrane-associated ERs expressed in GT1-7 neurons by physio-logical estradiol levels causes activation of a G, protein and modulates cAMP signaling and neuropeptide secretion. 相似文献
86.
Arora RC Hirsch GM Johnson Hirsch K Hancock Friesen C Armour JA 《American journal of physiology. Regulatory, integrative and comparative physiology》2001,280(6):R1736-R1740
We sought to determine the behavior of intrinsic cardiac neurons in human subjects undergoing cardiac surgery and to correlate their activity with hemodynamics status. A lead II electrocardiogram, pulmonary artery pressure, and systemic arterial pressure were recorded along with extracellular activity generated by right atrial neurons in 10 patients undergoing coronary artery bypass surgery. Identified neurons generated spontaneously activity that was, for the most part, unrelated to the cardiac cycle. Most neurons were activated by gentle mechanical distortion of ventricular epicardial loci. The activity generated by neurons in each patient increased when arterial pressure increased and decreased when arterial pressure fell. Intrinsic cardiac neurons continued to generate activity during cardioplegia and cardiopulmonary bypass, but at reduced levels. Normal neuronal activity was restored postbypass. It is concluded that human intrinsic cardiac neurons generate spontaneous activity and that many receive inputs from ventricular mechanosensory neurites. The latter may account for the fact that their behavior depends, in part, on cardiac dynamics. They are also sensitive to intravenously administered pharmacological agents. These data also indicate that cardiopulmonary bypass and cardioplegia do not induce residual depression of their function. 相似文献
87.
Backbone dynamics of free barnase and its complex with barstar determined by 15N NMR relaxation study 总被引:1,自引:1,他引:0
Backbone dynamics of uniformly 15N-labeled free barnase and its complex with unlabelled barstar have been studied at 40°C, pH 6.6, using 15N relaxation data obtained from proton-detected 2D {1H}-15N NMR spectroscopy. 15N spin-lattice relaxation rate constants (R1), spin-spin relaxation rate constants (R2), and steady-state heteronuclear {1H}-15N NOEs have been measured at a magnetic field strength of 14.1 Tesla for 91 residues of free barnase and for 90 residues out of a total of 106 in the complex (excluding three prolines and the N-terminal residue) backbone amide 15N sites of barnase. The primary relaxation data for both the cases have been analyzed in the framework of the model-free formalism using both isotropic and axially symmetric models of the rotational diffusion tensor. As per the latter, the overall rotational correlation times (m) are 5.0 and 9.5 ns for the free and complexed barnase, respectively. The average order parameter is found to be 0.80 for free barnase and 0.86 for the complex. However, the changes are not uniform along the backbone and for about 5 residues near the binding interface there is actually a significant decrease in the order parameters on complex formation. These residues are not involved in the actual binding. For the residues where the order parameter increases, the magnitudes vary significantly. It is observed that the complex has much less internal mobility, compared to free barnase. From the changes in the order parameters, the entropic contribution of NH bond vector motion to the free energy of complex formation has been calculated. It is apparent that these motions cause significant unfavorable contributions and therefore must be compensated by many other favorable contributions to effect tight complex formation. The observed variations in the motion and their different locations with regard to the binding interface may have important implications for remote effects and regulation of the enzyme action. 相似文献
88.
An efficient method has been developed for large-scale multiplication of Curculigo orchioides (Hypoxidaceae), an endangered medicinal plant, through direct bulbil formation from leaf explants in shake flask cultures. Leaf-segments (7 x 10 mm) were cultured in B5 liquid medium containing KNO3 (200 mgNL-1), (NH4)2SO4 (50 mgNL-1), benzyl adenosine (2.2 microM), adenine (0.11 mM), indole butyric acid (1.0 microM) and polyvinyl pyrrolidone (250 mgL-1). About 95% of explants produced maximum number of bulbils (546/flask at 6 weeks growth) in the medium. Shake flask cultures yielded 2737 bulbils/L medium whereas static cultures yielded 624 bulbils/L medium. Germination of bulbils was maximum (90.62%) on agar-gelled B5 medium containing benzyl adenosine (2.2 microM) and gibberellic acid (3.5 microM). Plantlets developed in vitro were successfully transferred to soil with a high rate of survivability (90%) and were comparable to natural population in growth and vigour. 相似文献
89.
90.
Testicular fine needle aspiration cytology for the diagnosis of azoospermia and oligospermia 总被引:1,自引:0,他引:1
Arora VK Singh N Bhatia A Rashmi Radhakrishnan G Jain BK Agarwal N 《Acta cytologica》2000,44(3):349-356
OBJECTIVE: To evaluate qualitative and quantitative cytologic features on testicular fine needle aspiration biopsy in the diagnosis of azoospermia and oligospermia and to correlate cytologic and histologic diagnoses. STUDY DESIGN: In this prospective study, 50 infertile males selected from the infertility clinic of Guru Tegh Bahadur Hospital were studied. Fine needle aspiration cytology (FNAC) smears from both testes of 27 azoospermic and 23 oligospermic patients (sperm count < 10 million per milliliter) were stained with May-Grünwald-Giemsa and Papanicolaou stain. Differential counting of 500 spermatogenic cells was done, and the number of Sertoli cells per 500 germ cells was determined for calculating the spermatic index and Sertoli cell index, respectively. FNAC and testicular biopsy were performed under local anesthesia as a minor surgical procedure. RESULTS: Six groups were identified on FNAC smears from azoospermic patients: I. normal spermatogenesis (8), II. hypospermatogenesis (2), III. maturation arrest (2), IV. Sertoli cells only (6), V. atrophic pattern (7), and VI. Leydig cell predominance (2). In oligospermic patients two groups were identified: I. those with normal spermatogenesis (4), and II. those with subnormal spermatogenesis (19). Correlation with histopathologic examination was seen in 81.5% azoospermic and 65.2% oligospermic patients. CONCLUSION: Qualitative and quantitative evaluation of testicular FNAC provides useful information on both azoospermic and oligospermic patients. FNAC performed under local anesthesia is an acceptable outpatient procedure that consistently yields sufficient diagnostic material in all patients. 相似文献