Publications by authors named "Satyendra Kumar"

83 Publications

Open-Ended Metallodithiolene Complexes with the 1,2,4,5-Tetrakis(diphenylphosphino)benzene Ligand: Modular Building Elements for the Synthesis of Multimetal Complexes.

Inorg Chem 2021 Sep 9;60(17):13177-13192. Epub 2021 Aug 9.

Department of Chemistry, Tulane University, 6400 Freret Street, New Orleans, Louisiana 70118, United States.

Open-ended, singly metalated dithiolene complexes with 1,2,4,5-tetrakis(diphenylphosphino)benzene (tpbz) are prepared either by ligand transfer to [ClM(tpbz)] from (RCS)SnR' (R = CN, R' = Me; R = Me, R' = Bu) or by a direct reaction between tpbz and [M(SCR)] (M = Ni, Pd, Pt; R = Ph, -anisyl) in a 1:1 ratio. The formation of dimetallic [(RCS)M(tpbz)M(SCR)] attends these syntheses in modest amounts, but the open-ended compounds are readily separated by silica chromatography. As affirmed by X-ray crystallographic characterization of numerous members of the set, the [(RCS)M(tpbz)] compounds show dithiolene ligands in their fully reduced ene-1,2-dithiolate form conjoined with divalent Group 10 ions. Minor amounts of octahedral [(PhCS)Pt(tpbz)], a presumed intermediate, are isolated from the preparation of [(PhCS)Pt(tpbz)]. Heterodimetallic [(PhCS)Pt(tpbz)Ni(SCMe)] is prepared from [(PhCS)Pt(tpbz)]; its cyclic voltammogram, upon anodic scanning, shows two pairs of closely spaced, but resolved, 1e oxidations corresponding first to [RCS] - 1e → [RCSS] and then to [RCSS] - 1e → [R(C═S)]. The open diphosphine of [(RCS)M(tpbz)] can be oxidized to afford open-ended [(RCS)M(tpbzE)] (E = O, S). Synthesis of the octahedral [(dppbO)Ni][I] [dppbO = 1,2-bis(diphenylphosphoryl)benzene] suggests that the steric profile of [(RCS)M(tpbzE)] is moderated enough that three could be accommodated as ligands around a metal ion.
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http://dx.doi.org/10.1021/acs.inorgchem.1c01573DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8424627PMC
September 2021

Soil spatial variability characterization: Delineating index-based management zones in salt-affected agroecosystem of India.

J Environ Manage 2021 Oct 13;296:113243. Epub 2021 Jul 13.

ICAR-Central Soil Salinity Research Institute, Karnal, 132001, Haryana, India.

Farm level recommendation in salt-affected agricultural landscapes is practically difficult due to spatial variations in inherent soil salinity, diverse farming situations and associated land ownerships with small-scale production systems. This study presents spatial array analysis of 354 geo-referenced soil samples revealing widespread heterogeneity in soil sodicity and fertility status across salt-affected Ghaghar basin of Kaithal district in Haryana, India. Six principal components accounted for 73% of the total variability, and the most important contributors [electrical conductivity (EC), sodium adsorption ratio (SAR), DTPA extractable copper (Cu) and boron (B), soil organic carbon (OC) and available phosphorus (AP)] as minimum data set were used to develop the soil quality index (SQI). Geostatistical analysis revealed Circular (EC and AP), Exponential (SAR, OC and B) and Gaussian (Cu) as the best fit semivariogram ordinary kriging model with weak to moderate spatial dependence. Three soil management zones (SMZs) were delineated by grouping the entire area based on soil quality index (SQI). Fertilizer recommendations for rice-wheat cropping system in different SMZs were calculated using soil test crop response (STCR) equation to ensure balanced fertilization, resource saving and reducing environmental footprints. Gypsum requirement map was prepared for systematic allocation and distribution, and enabling farmers to precisely use the mineral gypsum in order to reclaim and reduce stresses led by sodic lands. The implications of this study showed zone-specific advocacy for gypsum application (as soil ameliorant) and balanced fertilization in sustainable restoration of sodic lands, improving nutrient use efficiency and stabilizing crop production in salt-affected regions of India and similar ecologies elsewhere.
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http://dx.doi.org/10.1016/j.jenvman.2021.113243DOI Listing
October 2021

Deficit saline water irrigation under reduced tillage and residue mulch improves soil health in sorghum-wheat cropping system in semi-arid region.

Sci Rep 2021 01 21;11(1):1880. Epub 2021 Jan 21.

ICAR-Central Soil Salinity Research Institute, Karnal, Haryana, 132 001, India.

Judicious application of saline water except for critical growth stages, could be the only practical solution to meet the crop water demand in arid and semi-arid regions, due to limited access to freshwater, especially during dry winter months. A field experiment was conducted to study the effect of tillage [conventional (CT), reduced (RT), and zero (ZT)], rice straw mulch and deficit saline-water irrigation in wheat (100, 80 and 60% of wheat water requirement, CWR) followed by rainfed sorghum on soil properties and the yields of the cropping system. Yields of both the crops were comparable between RT and CT, but the wheat yield was reduced in ZT. The RT, mulching and deficit saline irrigation in wheat season (60% CWR) increased the sorghum fodder yield. Olsen's P (8.7-20.6%) and NHOAc-K (2.5-7.5%) increased in RT and ZT, respectively, over CT under both the crops. Deficit irrigation reduced soil salinity (EC) by 0.73-1.19 dS m after each crop cycle, while soil microbial biomass C (MBC) and N (MBN), dehydrogenase, urease and alkaline phosphatase reduced with an increase in EC. The α-glucosidase, MBC, EC, KMnOoxidizable N, and urease were identified as major contributors in developing the soil health index. Deficit irrigation (60% CWR) and rice straw mulching under ZT and RT showed higher values of soil health index. Overall, deficit saline-water irrigation under reduced tillage and straw mulching had the greatest potential in maintaining soil health, saving fresh irrigation water without affecting the productivity of the sorghum-wheat system in the semi-arid regions of India. Results also demonstrated that salt affected areas of arid and semiarid countries can replicate the protocol for indexing and screening of soil health indicators to assess the sustainability of a cropping system. This integrated management based on the nature of the available resources also provided a practical approach to achieve the target of land degradation neutrality and land restoration.
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http://dx.doi.org/10.1038/s41598-020-80364-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820430PMC
January 2021

Role of EEG in Predicting Outcome of Hepatic Encephalopathy Patients.

Neurodiagn J 2020 Dec 18;60(4):272-288. Epub 2020 Nov 18.

Department of Hepatology, Institute of Liver and Biliary Sciences , New Delhi, India.

A retrospective analysis of 151 patients with hepatic encephalopathy (HE) who were admitted to the liver intensive care unit (LICU) and liver transplant intensive care unit (TICU) and underwent electroencephalographic (EEG) testing was performed. We describe a method of grading the EEGs of patients with HE and predicting their subsequent outcomes. All liver failure patients with HE who underwent routine EEG testing in the LICU or TICU between October 1, 2018 and March 31, 2019, at the Institute of Liver and Biliary Sciences (ILBS) were enrolled in this analysis. The data was analyzed using Statistical Package for the Social Sciences (SPSS). The patients were divided into four grades of HE based on established EEG criteria (HE-EEG). One hundred fifty-one patients [127 Male (84%), 24 Female (16%)] with HE who underwent EEG testing were enrolled. Ages ranged from 3 to 74 years, with a mean age of 48.34 years and median interquartile range (IQR) of 49 years (38-60 years). Ninety-five patients (62.9%) had grade 1 and 2 hepatic encephalopathy, with a statistically significant, worse outcome seen in grades 3 and 4 HE patients. Seizures were seen in 30 (20.1%) of HE patients. Fifteen of 30 patients with seizures (50%) were in the ethanol and nonalcoholic steatohepatitis (NASH) groups. Forty-four of 59 (74.6%) MRIs and 35 of 60 (58.3%) CTs demonstrated some type of brain abnormality in these patients. Imaging abnormalities and the presence of seizures did not contribute to a statistically worse outcome. EEG has an important role in predicting the outcome and prognosis in HE. Patients with grade 3 or 4 HE-EEG, or with progressive worsening of HE-EEG grading were associated with the highest mortality rates.
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http://dx.doi.org/10.1080/21646821.2020.1824959DOI Listing
December 2020

Perceived Climate Variability and Compounding Stressors: Implications for Risks to Livelihoods of Smallholder Indian Farmers.

Environ Manage 2020 11 13;66(5):826-844. Epub 2020 Aug 13.

Krishi Vigyan Kendra, ICAR-Central Arid Zone Research Institute, Pali, Rajasthan, India.

Micro-scale perspectives are seldom included in planned climate change adaptations, yet farmers' perceptions can provide useful insights into livelihood impacts from interactions between climatic and other stressors. This research aims to understand how climate variability and other stressors are impacting the livelihoods of smallholder farmers in Azamgarh district, eastern Uttar Pradesh, India. Data from 84 smallholder farmers were collected using mixed qualitative and quantitative approaches, including interview and participatory methods, informed by multiple stressor and sustainable livelihood frameworks. Results revealed that farmers are increasingly facing problems caused by the reduced duration and number of rainy days, and erratic rainfall. Anomalies in seasonal cycles (longer summers, shorter winters) seem to have altered the local climate. Farmers reported that repeated drought impacts, even in years of moderate rainfall, are adversely affecting the rice crop, challenging the formal definition of drought. Climate variability, identified as the foremost stressor, often acts as a risk multiplier for ecological (e.g., soil sodicity), socio-economic (e.g., rising costs of cultivation) and political (e.g., mismatching policies and poor extension systems) stressors. In addition to climate stresses, resource-poor marginal groups in particular experienced higher risks resulting from changes in resource management regimes. This study provides an important cue to revisit the formal definitions of normal rainfall and drought, accommodating farmers' perceptions that evenly distributed rainfall, and not total rainfall is a key determinant of crop yields. Though India has developed adaptive measures for climate change and variability, integration of farmers' perceptions of climate and other stressors into such policies can improve the resilience of smallholder farmers, who have hitherto depended largely on autonomous adaptation strategies.
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http://dx.doi.org/10.1007/s00267-020-01345-xDOI Listing
November 2020

Investigating the Effect of Antibody-Antigen Reactions on the Internal Convection in a Sessile Droplet via Microparticle Image Velocimetry and DLVO Analysis.

Langmuir 2020 08 23;36(30):8826-8838. Epub 2020 Jul 23.

The evaporation of antigen-laden sessile droplets on antibody-immobilized PDMS substrates could be used in place of microwells for detection purposes owing to the lesser requirements of analytes and a reduced reaction time. To develop such techniques, the effects of different parameters on the reaction efficiency and on the resulting deposition patterns of antigens on the surface after evaporation need to be well understood. While the resultant deposition patterns from the evaporation of droplets of biological fluids on surfaces are being studied for various biomedical applications, systems where the analyte of interest in the droplet binds to the surface have not been investigated until now. While the effect of temperature on the internal convection within sessile droplets has been studied, the effect of the analyte (antigen in this work) concentration and the analyte-surface (antigen-antibody in this work) binding on the internal convection has not been studied until now. Therefore, to gain insight, the evaporation dynamics of sessile droplets with different concentrations of antigens along with polystyrene microspheres (used as tracers) in phosphate-buffered saline (PBS) on antibody-immobilized PDMS substrates were experimentally studied using microparticle image velocimetry (PIV). It was found that Marangoni flow due to concentration gradients and surface reactions was responsible for the observed velocity field. The antibody-antigen reaction (as compared to the control case of no surface reaction) and higher concentrations of prostate specific antigen (PSA) resulted in increased strength of Marangoni convection. To obtain further insight into the different deposition patterns obtained, the contributions of different particle-particle and particle-substrate forces were determined, and it was observed that the Marangoni forces along with surface tension and DLVO forces create a uniform deposition of the particles present within the droplet. This learning could be used to design biosensors.
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http://dx.doi.org/10.1021/acs.langmuir.0c01162DOI Listing
August 2020

Thermotropic Liquid-Crystalline and Light-Emitting Properties of Bis(4-aalkoxyphenyl) Viologen Bis(triflimide) Salts.

Molecules 2020 May 23;25(10). Epub 2020 May 23.

Division of Research, University at Albany, Albany, NY 12222, USA.

A series of bis(4-alkoxyphenyl) viologen bis(triflimide) salts with alkoxy chains of different lengths were synthesized by the metathesis reaction of respective bis(4-alkoxyphenyl) viologen dichloride salts, which were in turn prepared from the reaction of Zincke salt with the corresponding 4-n-alkoxyanilines, with lithium triflimide in methanol. Their chemical structures were characterized by H and C nuclear magnetic resonance spectra and elemental analysis. Their thermotropic liquid-crystalline (LC) properties were examined by differential scanning calorimetry, polarizing optical microscopy, and variable temperature X-ray diffraction. Salts with short length alkoxy chains had crystal-to-liquid transitions. Salts of intermediate length alkoxy chains showed both crystal-to-smectic A (SmA) transitions, Ts, and SmA-to-isotropic transitions, Ts. Those with longer length of alkoxy chains had relatively low Ts at which they formed the SmA phases that persisted up to the decomposition at high temperatures. As expected, all of them had excellent thermal stabilities in the temperature range of 330-370 °C. Their light-emitting properties in methanol were also included.
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http://dx.doi.org/10.3390/molecules25102435DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288076PMC
May 2020

pH-Based Detection of Target Analytes in Diluted Serum Samples Using Surface Plasmon Resonance Immunosensor.

Appl Biochem Biotechnol 2019 Apr 15;187(4):1272-1284. Epub 2018 Sep 15.

Department of Chemical Engineering, Kanpur, India.

Detection of minute quantities of target antigens in serum samples (consisting of a mixture of proteins/biomolecules) can be achieved by enhancement of the capture efficiencies of heterogeneous immunosensors. An important process parameter which affects the capture of target analytes in such immunosensors is the pH of the solution as the target proteins present in the serum samples are charged molecules. Here, we investigated the capture of prostate-specific antigens (PSAs), first in a mixed-analyte system wherein the solution contained two other non-specific proteins along with the target analyte, using the surface plasmon resonance spectroscopy. There are no reports on the detection of antigens in a mixed system based on the optimization of the pH values of the carrier fluid, and this is the motivation of the present work. Further, we studied interference effects caused by the presence of these non-specific proteins in the mixed-analyte systems by artificially increasing the ratio of the interfering proteins to that of the target protein. Eventually PSA spiked into the rabbit serum samples was captured through the optimization of the pH of the solution. We could detect PSA in the serum samples when diluted to 100 times or more, where the amounts of other interfering proteins were ~ 66 times that of the amount of PSA. This study proposes a heterogeneous immunosensor to detect the target analytes in the diluted serum samples by tuning pH the of solution mixture, which can be utilized to detect disease biomarkers in serum samples.
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http://dx.doi.org/10.1007/s12010-018-2883-3DOI Listing
April 2019

Anomalous Nanoscale Optoacoustic Phonon Mixing in Nematic Mesogens.

J Phys Chem Lett 2018 May 2;9(10):2546-2553. Epub 2018 May 2.

Neutron Scattering Directorate , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States.

Recent inelastic X-ray scattering (IXS) experiments on mesogens have revealed entirely new capabilities with regards to their nanoscale phonon-assisted heat management. Mesogens such as nematic liquid crystals (LCs) are appealing systems for study because their structure and morphology can easily be tuned. We report on Q-resolved ultra-high-resolution IXS, X-ray diffraction, and THz time-domain spectroscopy experiments combined with large-scale all-atom molecular dynamics simulations on the dynamic properties of 5CB LCs. For the first time, we observe a strong mixing of phonon excitations originating from independent in-phase and out-of-phase van-der-Waals-mediated displacement patterns. The coexistence of transverse acoustic and optical modes of 5CB LCs at near room temperature is revealed through the emergent transverse phonon gap and THz light-phonon coupling taking place within the same energy range. Furthermore, our experimental observations are supported by analysis showing correlations of spontaneous fluctuations of LCs on picosecond time scales. These findings are significant for the design of a new generation of soft molecular vibration-sensitive nanoacoustic and optomechanical applications.
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http://dx.doi.org/10.1021/acs.jpclett.8b00926DOI Listing
May 2018

Emergent Optical Phononic Modes upon Nanoscale Mesogenic Phase Transitions.

Nano Lett 2017 06 2;17(6):3870-3876. Epub 2017 Jun 2.

National Synchrotron Light Source II, Brookhaven National Laboratory , Upton, New York 11973, United States.

The investigation of phononic collective excitations in soft matter systems at the molecular scale has always been challenging due to limitations of experimental techniques in resolving low-energy modes. Recent advances in inelastic X-ray scattering (IXS) enabled the study of such systems with unprecedented spectral contrast at meV excitation energies. In particular, it has become possible to shed light on the low-energy collective motions in materials whose morphology and phase behavior can easily be manipulated, such as mesogenic systems. The understanding of collective mode behavior with a Q-dependence is the key to implement heat management based on the control of a sample structure. The latter has great potential for a large number of energy-inspired innovations. As a first step toward this goal, we carried out high contrast IXS measurements on a liquid crystal sample, D7AOB, which exhibits solid-like dynamic features, such as the coexistence of longitudinal and transverse phononic modes. For the first time, we found that these terahertz phononic excitations persist in the crystal, smectic A, and isotropic phases. Furthermore, the intermediate smectic A phase is shown to support a van der Waals-mediated nonhydrodynamic mode with an optical-like phononic behavior. The tunability of the collective excitations at nanometer-terahertz scales via selection of the sample mesogenic phase represents a new opportunity to manipulate optomechanical properties of soft metamaterials.
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http://dx.doi.org/10.1021/acs.nanolett.7b01324DOI Listing
June 2017

Phase behavior and characterization of heptamethyltrisiloxane-based de Vries smectic liquid crystal by electro-optics, x rays, and dielectric spectroscopy.

Phys Rev E 2017 Mar 10;95(3-1):032701. Epub 2017 Mar 10.

Department of Physics, Kent State University, Kent, Ohio 44242, USA.

A heptamethyltrisiloxane liquid crystal (LC) exhibiting I-SmA^{*}-SmC^{*} phases has been characterized by calorimetry, polarizing microscopy, x-ray diffraction, electro-optics, and dielectric spectroscopy. Observations of a large electroclinic effect, a large increase in the birefringence (Δn) with electric field, a low shrinkage in the layer thickness (∼1.75%) at 20 °C below the SmA^{*}-SmC^{*} transition, and low values of the reduction factor (∼0.40) suggest that the SmA^{*} phase in this material is of the de Vries type. The reduction factor is a measure of the layer shrinkage in the SmC^{*} phase and it should be zero for an ideal de Vries. Moreover, a decrease in the magnitude of Δn with decreasing temperature indicates the presence of the temperature-dependent tilt angle in the SmA^{*} phase. The electro-optic behavior is explained by the generalized Langevin-Debye model as given by Shen et al. [Y. Shen et al., Phys. Rev. E 88, 062504 (2013)10.1103/PhysRevE.88.062504]. The soft-mode dielectric relaxation strength shows a critical behavior when the system goes from the SmA^{*} to the SmC^{*} phase.
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http://dx.doi.org/10.1103/PhysRevE.95.032701DOI Listing
March 2017

Palladacycles of sulfated and selenated Schiff bases of ferrocene-carboxaldehyde as catalysts for O-arylation and Suzuki-Miyaura coupling.

Dalton Trans 2017 Feb;46(8):2485-2496

Department of Chemistry, Indian Institute of Technology, Delhi, New Delhi 110016, India.

Schiff base ligands (L1: sulfated and L2: selenated) having a ferrocene core synthesized by reacting ferrocene-carboxaldehyde with 2-(phenylthio/seleno)ethylamine on treatment with NaPdCl in the presence of NaOAc give cyclopalladated complexes [Pd(L1/L2-H)Cl] (1/2). Complex 1 of a sulfated Schiff base L1, on reacting with one equivalent of triphenylphosphine gives complex [Pd(L1-H)PPhCl] (3), formed due to cleavage of a Pd-S bond. With 2 such a reaction does not occur, as a Pd-Se bond being stronger than that of its sulfur analogue does not get cleaved. L1, L2 and their complexes 1-3 were authenticated with HR-MS, H, C{H} and Se{H} NMR spectroscopy. The single crystal structures of 1-3 were determined with X-ray diffraction. Palladium in all three complexes has nearly a square planar geometry. The Pd-S, Pd-Se and Pd-P bond distances are 2.4249(12), 2.5058(14) and 2.2445(17) Å respectively. The catalytic activity of complexes 1-3 was explored for O-arylation of phenol and Suzuki-Miyaura coupling (SMC) of phenylboronic acid with aryl bromides and chlorides. The optimum reaction time for SMC of ArBr is 3 h whereas for ArCl it is 6 h. The TON values of O-arylation catalyzed with complexes 1-3 are up to ∼170 (TOF, 28 h) and SMC ∼9300 (TOF, 3100 h) for the reaction time of the order of 3 and 6 h respectively. The catalytic process is somewhat more efficient with 2 (Pd bonded with a selenoether group), than 3, followed by 1.
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http://dx.doi.org/10.1039/c7dt00083aDOI Listing
February 2017

X-ray and Raman scattering study of orientational order in nematic and heliconical nematic liquid crystals.

Phys Rev E 2016 Dec 13;94(6-1):060701. Epub 2016 Dec 13.

Department of Physics, Kent State University, Kent, Ohio 44242, USA.

The temperature dependence of the orientational order parameters 〈P_{2}(cosβ)〉 and 〈P_{4}(cosβ)〉 in the nematic (N) and twist-bend nematic (N_{tb}) phases of the liquid crystal dimer CB7CB have been measured using x-ray and polarized Raman scattering. The 〈P_{2}(cosβ)〉 obtained from both techniques are the same, while 〈P_{4}(cosβ)〉, determined by Raman scattering is, as expected, systematically larger than its x-ray value. Both order parameters increase in the N phase with decreasing temperature, drop across the N-N_{tb} transition, and continue to decrease. In the N_{tb} phase, the x-ray value of 〈P_{4}(cosβ)〉 eventually becomes negative, providing a direct and independent confirmation of a conical molecular orientational distribution. The heliconical tilt angle α, determined from orientational distribution functions in the N_{tb} phase, increases to ∼24^{∘} at ∼15 K below the transition. In the N_{tb} phase, α(T)∝(T^{*}-T)^{λ}, with λ=0.19±0.03. The transition supercools by 1.7 K, consistent with its weakly first-order nature. The value of λ is close to 0.25 indicating close proximity to a tricritical point.
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http://dx.doi.org/10.1103/PhysRevE.94.060701DOI Listing
December 2016

Clinical validation of efficacy and safety of herbal cough formulation "Honitus syrup" for symptomatic relief of acute non-productive cough and throat irritation.

Ayu 2016 Jul-Dec;37(3-4):206-214

Medical Affairs and Clinical Research Division, Principal Scientist - Healthcare Research, Healthcare Research, Dabur Research and Development Centre, Dabur India Limited, Sahibabad (Ghaziabad), UP, India.

Background: Acute cough represents the most common illness evaluated in the outpatient settings. Available remedies for its management are generally allopathic combinations of antihistamines and decongestants that achieve antitussive activity, but often with unpleasant side effects prompting the need to explore safer and effective options. Honitus is an Ayurvedic proprietary herbal cough syrup with benefits of honey, intended to provide relief in acute nonproductive cough and throat irritation without causing drowsiness. This study investigated the safety and efficacy of Honitus in reducing acute nonproductive cough and throat irritation in comparison to a standard marketed allopathic cough syrup intended for use in similar conditions.

Materials And Methods: This was a randomized double-blind study conducted in 105 individuals who received orally 2 tsp (10 ml) of either Honitus or marketed cough syrup (MCS) four times a day for 3 days. Response to treatment was evaluated from baseline to the end of treatment period on the basis of changes in day and night frequencies of cough, throat irritation and development of adverse events (AEs).

Results: Honitus was found safe and effective in reducing symptoms of acute nonproductive cough, throat irritation, and comparable to MCS in reducing day and night frequencies of cough, the time to relief from cough and throat irritation and the Physician's Global Assessment of cough. Honitus showed comparably better results than MCS on throat irritation, the duration of relief from cough and throat irritation without causing drowsiness. No AEs related to study or study products were reported.

Conclusion: Honitus Syrup is safe and effective in reducing the symptoms of acute nonproductive cough and throat irritation without causing drowsiness.
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http://dx.doi.org/10.4103/ayu.AYU_156_15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5822975PMC
March 2018

'Click' generated 1,2,3-triazole based organosulfur/selenium ligands and their Pd(ii) and Ru(ii) complexes: their synthesis, structure and catalytic applications.

Dalton Trans 2016 Jul 24;45(28):11445-58. Epub 2016 Jun 24.

Department of Chemistry, Indian Institute of Technology Delhi, New Delhi-110016, India.

1-(2,6-Diisopropylphenyl)-4-(phenylthio/selenomethyl)-1H-1,2,3-triazole (L1/L2) was synthesized by a 'Click' reaction and treated with [Pd(CH3CN)2Cl2] for 5 h or [(η(6)-C6H6)RuCl(μ-Cl)]2 for 8 h (followed by reaction with NH4PF6) at room temperature, resulting in complexes [Pd(L)Cl2] (1 and 2) or [(η(6)-C6H6)Ru(L)Cl]PF6 (3 and 4) (L = L1 or L2), respectively. The four complexes (1-4) and ligands (L1 and L2) were characterized with (1)H, (13)C{(1)H} and (77)Se{(1)H} NMR spectroscopy and high resolution mass spectrometry. The single crystal structures of 1-4 were solved. The geometry of Pd in 1 and 2 is distorted square planar. The Pd-S and Pd-Se bond distances in 1 and 2 are 2.277(3) and 2.384(6) Å respectively. In 3 and 4, there is a pseudo-octahedral "piano-stool" type disposition of donor atoms around Ru. The Ru-S and Ru-Se bond lengths in 3 and 4 are 2.3728(12) and 2.4741(6) Å respectively. The catalytic activity of complexes 1 and 2 was explored for Suzuki-Miyaura coupling (SMC) in water and the Sonogashira coupling reaction. For various aryl bromides, including deactivated ones, complexes 1 and 2 were found to be efficient catalysts for both couplings. The optimum loading of 1 and 2 required to catalyze both coupling reactions is of the order of 0.001-2 mol% of Pd. For SMC, no additive or phase transfer catalyst was added. For catalysis of the transfer hydrogenation (TH) of aldehydes and ketones, the half-sandwich Ru(ii) complexes 3 and 4 were explored. Their optimum catalytic loading was found to be 0.1-0.4 mol% of Ru. For TH, both the water solvent and the glycerol hydrogen source are environmentally friendly. The catalytic efficiencies of 3 and 4 are comparable with those reported for other catalysts for TH carried out with 2-propanol or glycerol as a H-source. 1, with a sulfur ligand, is more efficient than 2 (Se analog) for both SMC and the Sonogashira coupling. The activities of 3 and 4 for TH are in the order Se > S.
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http://dx.doi.org/10.1039/c6dt01406bDOI Listing
July 2016

Emissivity and electrooptical properties of semiconducting quantum dots/rods and liquid crystal composites: a review.

Rep Prog Phys 2016 05 18;79(5):056502. Epub 2016 Apr 18.

Department of Physics, Kent State University, Kent OH 44242, USA.

Investigations of the mixtures of semiconducting quantum scale particles in anisotropic liquid crystal (LC) medium have become a vibrant area of research primarily due to their very interesting phenomenology. The results of these investigations fall into four groups: (i) Photoluminescent emissive properties of the quantum particles ordinarily depend on the size, shape, and chemical nature of the particles. These undergo important changes in their spectrum, polarization, and isotropy of emission when dissolved in an anisotropic LC phase. Moreover, their response to external stimuli such as mechanical, optical, or electric fields is altered in important ways; (ii) physical properties of LCs such as viscosity, dielectric relaxation, etc are modified by the addition of quantum particles. Their presence in ferroelectric smectic LC is known to give rise to an antiferro- to ferri-electric phase transition and suppresses the paraelectric phase; (iii) switching characteristics of LC devices are altered in important ways by the addition of quantum particles. Their threshold voltage is usually lowered, contrast ratio, and switching speed of nematic, ferroelectric, and cholesteric devices may increase or decrease depending on the concentration, applied field, and particle anisotropy; and (iv) controlled aggregation of quantum particles at the interface between isotropic and LC domains, near added polystyrene beads, and in the vicinity of point defects gives rise to interesting photonic structures, enables studies of photon antibunching and single photon sources. Clearly, there is a need to understand the basic and applied aspects of these systems and find routes to their technological applications including sensors, electrooptical devices, and solar energy harvesting. This review provides an overview of recent work involving liquid crystals and a variety of quantum particles.
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http://dx.doi.org/10.1088/0034-4885/79/5/056502DOI Listing
May 2016

Reversible Isothermal Twist-Bend Nematic-Nematic Phase Transition Driven by the Photoisomerization of an Azobenzene-Based Nonsymmetric Liquid Crystal Dimer.

J Am Chem Soc 2016 04 19;138(16):5283-9. Epub 2016 Apr 19.

Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen , Meston Building, Old Aberdeen AB24 3UE, United Kingdom.

The liquid crystal nonsymmetric dimer, 1-(4-butoxyazobenzene-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OABOBu), shows enantiotropic twist-bend nematic, NTB, and nematic, N, phases. The NTB phase has been confirmed using polarized light microscopy, freeze fracture transmission electron microscopy, and X-ray diffraction. The helicoidal pitch in the NTB phase is 18 nm. The NTB-N (TNTBN) and N-I (TNI) transition temperatures are reduced upon UV light irradiation, with the reduction in TNTBN being much larger than that in TNI. An isothermal, reversible NTB-N transition may be driven photochemically. These observations are attributed to a trans-cis photoisomerization of the azobenzene fragment on UV irradiation, with the cis isomers stabilizing the standard nematic phase and the trans isomers stabilizing the NTB phase. The dramatic changes in TNTBN provide evidence that the transition between the normal nematic and twist-bend nematic with spontaneous breaking of chiral symmetry is crucially dependent on the shape of molecular dimers, which changes greatly during the trans-cis isomerization.
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http://dx.doi.org/10.1021/jacs.5b13331DOI Listing
April 2016

Smectic-A and Hexatic-B Liquid Crystal Phases of Sanidic Alkyl-Substituted Dibenzo[fg,op]naphthacenes.

J Phys Chem B 2016 Mar 7;120(10):2829-37. Epub 2016 Mar 7.

Department of Chemistry & Biochemistry, Miami University , Oxford, Ohio 45056, United States.

Despite longstanding interest in liquid crystalline compounds with simple rod- or disc-like shapes (calamitics or discotics), very few examples of the analogous board-shaped, or "sanidic", liquid crystals exist. A new series of alkyl-substituted dibenzo[fg,op]naphthacenes have been prepared by planarization of o-phenylene precursors through dehydrohalogenation. Their photophysical properties have been studied in dichloromethane. Liquid crystal phase behavior was characterized by polarized optical microscopy, differential scanning calorimetry, and X-ray diffraction. All of the compounds exhibit monotropic liquid crystal phases on cooling from the isotropic phase. The compounds with shorter alkyl (pentyl and heptyl) chains exhibit the uniaxial smectic-A phase analogous to that of simple calamitic mesogens. The compounds with longer alkyl (nonyl, undecyl, and tridecyl) chains exhibit a new smectic liquid crystal phase featuring short-range positional order with an apparent rectangular lattice in the smectic layers, that is, an orthogonal biaxial hexatic-B. The molecular arrangement in this phase likely corresponds to a distorted herringbone packing of the board-shaped structures. Further, the compound with nonyl chains exhibits an underlying smectic-B phase. DFT calculations show that the cores of the mesogens are twisted into C2-symmetric saddle-shaped geometries because of steric interactions along their rims. The liquid crystal phases and their structures are discussed in the context of the compounds' board-like shapes and intercore interactions.
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http://dx.doi.org/10.1021/acs.jpcb.5b10990DOI Listing
March 2016

AID hits the jackpot when missing the target.

Curr Opin Immunol 2016 Apr 1;39:96-102. Epub 2016 Feb 1.

Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL, USA.

Activation induced deaminase is the single B cell specific factor mediating class switch recombination and somatic hypermutation. Numerous studies have shown that AID preferentially targets Ig substrates and also attacks non-Ig substrates to create DNA damage that contributes to lymphomagenesis. AID targeting to Ig loci is linked to transcription but the mechanism governing this process has been obscure. Here we discuss research that illustrates the connection between AID targeting to DNA substrates and transcription processes to reveal rules governing the specificity of AID attack. These observations are woven together to provide a integrated view of AID function and a surprising linkage with global regulation of gene expression.
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http://dx.doi.org/10.1016/j.coi.2016.01.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979549PMC
April 2016

Signal Amplification in Field Effect-Based Sandwich Enzyme-Linked Immunosensing by Tuned Buffer Concentration with Ionic Strength Adjuster.

Appl Biochem Biotechnol 2016 Apr 22;179(1):168-78. Epub 2016 Jan 22.

Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.

Miniaturization of the sandwich enzyme-based immunosensor has several advantages but could result in lower signal strength due to lower enzyme loading. Hence, technologies for amplification of the signal are needed. Signal amplification in a field effect-based electrochemical immunosensor utilizing chip-based ELISA is presented in this work. First, the molarities of phosphate buffer saline (PBS) and concentrations of KCl as ionic strength adjuster were optimized to maximize the GOx glucose-based enzymatic reactions in a beaker for signal amplification measured by change in the voltage shift with an EIS device (using 20 μl of solution) and validated with a commercial pH meter (using 3 ml of solution). The PBS molarity of 100 μM with 25 mM KCl provided the maximum voltage shift. These optimized buffer conditions were further verified for GOx immobilized on silicon chips, and similar trends with decreased PBS molarity were obtained; however, the voltage shift values obtained on chip reaction were lower as compared to the reactions occurring in the beaker. The decreased voltage shift with immobilized enzyme on chip could be attributed to the increased Km (Michaelis-Menten constant) values in the immobilized GOx. Finally, a more than sixfold signal enhancement (from 8 to 47 mV) for the chip-based sandwich immunoassay was obtained by altering the PBS molarity from 10 to 100 μM with 25 mM KCl.
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http://dx.doi.org/10.1007/s12010-016-1986-yDOI Listing
April 2016

Hepatoprotective activity of a new polyherbal formulation against paracetamol and D-galactosamine induced hepatic toxicity.

J Pharm Bioallied Sci 2015 Oct-Dec;7(4):246-9

Dabur Research and Development Center, Dabur India Ltd., Sahibabad, Ghaziabad, Uttar Pradesh, India.

Objective: The present study was envisaged to evaluate the protective effect of polyherbal formulation, DRDC/AY/8060, developed by Dabur India Ltd., against paracetamol and D-galactosamine induced hepatic toxicities in Wistar rats.

Materials And Methods: The study was carried out in two different experiments of 10 and 14 days against paracetamol and D-galactosamine, respectively. Animals were divided into different treatment groups (n = 6). The control group received normal saline, a toxicant group in two experiments received paracetamol 750 mg/kg p.o. every 72 h for 10 days and D-galactosamine 400 mg/kg i.p. single dose. The test formulation was used at the two dose levels of 120 and 240 mg/kg/day. Treatment groups treated with test formulations were also administered D-galactosamine as given in toxicant group. At the end of the dosing schedule, blood was withdrawn from the retrobulbar plexus of the animals for serum estimation of serum glutamate oxaloacetate transferase (SGOT), serum glutamate pyruvate trasnferase (SGPT), albumin, bilirubin, and alkaline phosphatase (ALP). Following the withdrawal of blood animals was sacrificed, and liver tissue was excised for estimation of thiobarbituric acid reactive substances (lipid peroxidation, malondialdehyde), tissue glutathione (GSH) and histopathological studies.

Results: It was evident from the biochemical estimation that both paracetamol and galactosamine caused hepatotoxicity in the toxicant groups. However, treatment with DRDC/AY/8060 significantly (P < 0.001, vs. toxicant) reduced the levels of SGOT, SGPT, serum bilirubin, and ALP, as well as decreased lipid peroxidation. In addition, treatment with test formulation also significantly (P < 0.001, vs. toxicant) elevated serum albumin and GSH levels compared to toxicant groups.

Conclusion: On the basis of these studies and comparative evaluation it can be concluded that the formulation DRDC/AY/8060 showed hepatoprotective activity against paracetamol and D-galactosamine at 120 mg/kg and 240 mg/kg.
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http://dx.doi.org/10.4103/0975-7406.168018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4678983PMC
December 2015

Evaluation of Ratnaprash for its effect on strength, stamina and fatigue using swim endurance test and biochemical estimation in swiss albino mice.

Anc Sci Life 2015 Jul-Sep;35(1):26-31

Healthcare Research, Dabur Research and Development Centre, Sahibabad (Ghaziabad), Uttar Pradesh, India.

Context: Traditional medicines have been considered as important resources for postponing fatigue, accelerating elimination of fatigue related metabolites and improving physical ability. Rasāyanās or rejuvenative therapies are mentioned as one of the eight clinical specialties in Ayurveda for attaining longevity, healthy life and regulation of bodily balance. Eventhough more detailed studies are needed to confirm the claims of benefits in the light of evidence based research, Ratnaprash, a herbo-mineral rasāyana formulation, is proposed here to be an antifatigue supplement that is good in promoting strength and stamina.

Materials And Methods: In the present study, anti fatigue, strength and stamina enhancing properties of Ratnaprash were examined based on swim endurance capacity and the change in biochemical parameters in Swiss Albino mice. Treatment groups were orally administered Ratnaprash at various test doses (500, 1000, 2000 mg/Kg per day), while the control group received distilled water at similar dose volumes. Effect of therapy was evaluated after 28 days of treatment.

Results: At the end of study period, the swimming times to exhaustion were longer in the treated groups than in the control group. Plasma lactate levels of treated groups were lower than those of the control group (P < 0.05) while tissue ATP levels were higher. These effects were dose dependent and the strongest effect was seen in groups treated at 1000 mg/Kg.

Conclusion: Ratnaprash enhanced the forced swimming capacity of mice and exhibited elevated anti-fatigue activity, reduced blood lactate levels and increased tissue ATP levels in preclinical models in comparison to vehicle control, exhibiting possible role in increasing strength and stamina and contributing anti-fatigue activity.
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http://dx.doi.org/10.4103/0257-7941.165626DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4623629PMC
November 2015

Complexes of (η(6)-benzene)ruthenium(II) with 1,4-bis(phenylthio/seleno-methyl)-1,2,3-triazoles: synthesis, structure and applications in catalytic activation of oxidation and transfer hydrogenation.

Dalton Trans 2015 Nov 19;44(44):19141-52. Epub 2015 Oct 19.

Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016, India.

1,4-Bis(phenylthio/seleno methyl)-1,2,3-triazoles (L1-L4) synthesized by a 'Click' reaction react with [{(η(6)-C6H6)RuCl(μ-Cl)}]2 and NH4PF6 resulting in complexes [(η(6)-C6H6)RuClL]PF6 (1-4 for L = L1-L4) in which the ligands coordinate in a bidentate mode through S/Se and N of triazole. The CH2EPh (E = S or Se) attached to nitrogen of triazole remains pendent. Ligands and complexes have been authenticated with multinuclei NMR, IR and HR-MS. Single crystal structures of complexes 1-4 have been solved. The Ru-S and Ru-Se bond lengths (Å) are respectively 2.388(2)/2.3902(19) and 2.5007(4)/2.5262(19). The disposition of benzene ring, N, S/Se and Cl around Ru is of a piano stool type. For catalytic oxidation of alcohols [Oppenauer-type and with N-methylmorpholine-N-oxide (NMO)] and transfer hydrogenation (TH) of carbonyl compounds [with 2-propanol and glycerol] all the four complexes have been found efficient. The optimum catalyst loadings (in mol%) are: 0.01 (NMO), 0.1 (Oppenauer), 0.01 (TH with 2-propanol) and 0.5 (TH with glycerol). Interestingly, time profiles (under optimum conditions) of two catalytic oxidations and TH's are almost similar, suggesting that they are competitive on appropriate catalyst loading. DFT calculations are consistent with somewhat low reactivity of 1 in comparison to those of 2-4.
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http://dx.doi.org/10.1039/c5dt02926kDOI Listing
November 2015

NIR light-directing self-organized 3D photonic superstructures loaded with anisotropic plasmonic hybrid nanorods.

Chem Commun (Camb) 2015 Oct;51(81):15039-42

Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, USA.

Self-organized 3D photonic superstructures loaded with plasmonic hybrid nanorods were found to undergo structural transformation from body-centered cubic to simple cubic upon NIR-light irradiation resulting from the "photothermal effect" of gold nanorods. Furthermore, dynamic NIR light-directed red, green and blue reflections of the nanocomposites were demonstrated.
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http://dx.doi.org/10.1039/c5cc06146fDOI Listing
October 2015

Near infrared light-driven liquid crystal phase transition enabled by hydrophobic mesogen grafted plasmonic gold nanorods.

Chem Commun (Camb) 2015 Jun;51(48):9845-8

Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA.

Light-driven phase transition in liquid crystals is a fascinating endeavour from both scientific and technological points of view. Here we demonstrate the proof-of-principle that the photothermal effect of organo-soluble plasmonic gold nanorods can introduce the phase transition of thermotropic liquid crystals upon near infrared laser irradiation. Interestingly, the reverse process occurs when the laser is switched off.
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http://dx.doi.org/10.1039/c5cc02127hDOI Listing
June 2015

Palladium(II)-1-phenylthio-2-arylchalcogenoethane complexes: palladium phosphide nano-peanut and ribbon formation controlled by chalcogen and Suzuki coupling activation.

Dalton Trans 2015 Apr;44(14):6600-12

Department of Chemistry, Indian Institute of Technology Delhi, New Delhi-110016, India.

The ligands PhSCH2CH2EAr (; E = S, Se or Te) and their Pd-complexes [PdLCl2] () have been synthesized and authenticated with their (1)H, (13)C{(1)H}, (77)Se{(1)H} and (125)Te{(1)H} NMR spectra. Single crystal structures of and reveal the geometry of donor atoms around palladium as nearly square planar. Thermolysis of all three complexes in trioctylphosphine (TOP) at 350, 320 and 280 °C, respectively, results in a single phase of crystalline PdP2. The morphology of the phase varies with 'E' to some extent. The nanopeanuts (size ∼30 and ∼35 nm) were formed with and as precursor complexes. On using complex as a precursor nanoribbons are formed. The preferential growth in the (202) plane in the case of all the three precursor complexes has been rationalized in terms of texture coefficient and average crystallite size. All three complexes and PdP2 NPs have been explored for Suzuki-Miyaura coupling of several aryl halides. Complexes and show good catalytic activity but complex does not. The activity appears to result due to in situ generated palladium containing nanoparticles (NPs) in the case of and . The formation of inactive large Pd aggregates in the case of appears to be responsible for the difference. The PdP2 NPs have been found to show good catalytic activity and recyclability up to six reaction cycles. The results of the three phase test suggest the involvement of both homogeneous and heterogeneous pathways in the activation of Suzuki coupling. DFT based free energy calculations are consistent with the results of catalysis via Pd(0) protected with the ligand. This palladium may also be released from in situ generated NPs. In the case of , negligible reactivity may be due to non-release of Pd.
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http://dx.doi.org/10.1039/c4dt03471fDOI Listing
April 2015

Development and Validation of GC-ECD Method for the Determination of Metamitron in Soil.

Int J Anal Chem 2015 5;2015:592763. Epub 2015 Feb 5.

Department of Chemistry (Division of Agricultural Chemicals), College of Basic Sciences and Humanities, G. B. Pant University of Agriculture and Technology, Pantnagar 263145, India.

This paper aims at developing and validating a convenient, rapid, and sensitive method for estimation of metamitron from soil samples.Determination andquantification was carried out by Gas Chromatography on microcapillary column with an Electron Capture Detector source. The compound was extracted from soil using methanol and cleanup by C-18 SPE. After optimization, the method was validated by evaluating the analytical curves, linearity, limits of detection, and quantification, precision (repeatability and intermediate precision), and accuracy (recovery). Recovery values ranged from 89 to 93.5% within 0.05- 2.0 µg L(-1) with average RSD 1.80%. The precision (repeatability) ranged from 1.7034 to 1.9144% and intermediate precision from 1.5685 to 2.1323%. Retention time was 6.3 minutes, and minimum detectable and quantifiable limits were 0.02 ng mL(-1) and 0.05 ng g(-1), respectively. Good linearity (R (2) = 0.998) of the calibration curves was obtained over the range from 0.05 to 2.0 µg L(-1). Results indicated that the developed method is rapid and easy to perform, making it applicable for analysis in large pesticide monitoring programmes.
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http://dx.doi.org/10.1155/2015/592763DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4334928PMC
March 2015

Constraints contributed by chromatin looping limit recombination targeting during Ig class switch recombination.

J Immunol 2015 Mar 26;194(5):2380-9. Epub 2015 Jan 26.

Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, IL 60612; and

Engagement of promoters with distal elements in long-range looping interactions has been implicated in regulation of Ig class switch recombination (CSR). The principles determining the spatial and regulatory relationships among Igh transcriptional elements remain poorly defined. We examined the chromosome conformation of C region (CH) loci that are targeted for CSR in a cytokine-dependent fashion in mature B lymphocytes. Germline transcription (GLT) of the γ1 and ε CH loci is controlled by two transcription factors, IL-4-inducible STAT6 and LPS-activated NF-κB. We showed that although STAT6 deficiency triggered loss of GLT, deletion of NF-κB p50 abolished both GLT and γ1 locus:enhancer looping. Thus, chromatin looping between CH loci and Igh enhancers is independent of GLT production and STAT6, whereas the establishment and maintenance of these chromatin contacts requires NF-κB p50. Comparative analysis of the endogenous γ1 locus and a knock-in heterologous promoter in mice identified the promoter per se as the interactive looping element and showed that transcription elongation is dispensable for promoter/enhancer interactions. Interposition of the LPS-responsive heterologous promoter between the LPS-inducible γ3 and γ2b loci altered GLT expression and essentially abolished direct IgG2b switching while maintaining a sequential μ→γ3→γ2b format. Our study provides evidence that promoter/enhancer looping interactions can introduce negative constraints on distal promoters and affect their ability to engage in germline transcription and determine CSR targeting.
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http://dx.doi.org/10.4049/jimmunol.1401170DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4440573PMC
March 2015

Dual relaxation and structural changes under uniaxial strain in main-chain smectic-C liquid crystal elastomer.

Phys Chem Chem Phys 2015 Jan;17(1):191-9

Department of Physics, Kent State University, Kent, OH 44242, USA.

The relationship between strain-dependent macroscopic elastic behavior and the changes in microscopic structure of the smectic-C liquid crystal elastomer (LCE), C11MeHQSi8 were investigated using synchrotron X-ray studies. At very low strains ε ≤ 0.2, the smectic layers are randomly oriented. As the strain increases beyond 0.2, the smectic layers reorient and become parallel to the direction of the applied strain. The polydomain to monodomain (P-M) transition accompanied by the formation of chevron structure ensues for ε > 0.2 and is nearly complete for ε = 0.7. The chevron structure relaxes after the applied strain changes, with a time constant τα ∼ 45 min while the orientation order parameters of the mesogenic and elastomeric components gradually increase and saturate at 0.83 and 0.4, respectively at ε = 1.7 which is near the end of the plateau region. Relaxation rates τα for the tilt angle and τd corresponding to the smectic layer spacing both become about 10 times faster when the strain exceeds 0.7. The LCE remains "locked" into the monodomain state and retains 90% and 80% values of α and S, respectively for 24 hours after the applied strain is removed. The viscoelastic properties of the liquid crystal appear to dominate the equilibration process at low strains while the elastomeric properties control the system's response at high strains.
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http://dx.doi.org/10.1039/c4cp04713cDOI Listing
January 2015
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