Publications by authors named "Zhaohua Dai"

16 Publications

  • Page 1 of 1

Modeling impacts of drought-induced salinity intrusion on carbon dynamics in tidal freshwater forested wetlands.

Ecol Appl 2022 Jun 25:e2700. Epub 2022 Jun 25.

U. S. Geological Survey, Wetland and Aquatic Research Center, Lafayette, Louisiana, USA.

Tidal freshwater forested wetlands (TFFW) provide critical ecosystem services including essential habitat for a variety of wildlife species and significant carbon sinks for atmospheric carbon dioxide. However, large uncertainties remain concerning the impacts of climate change on the magnitude and variability of carbon fluxes and storage across a range of TFFW. In this study, we developed a process-driven Tidal Freshwater Wetlands DeNitrification-DeComposition model (TFW-DNDC) that has integrated new features, such as soil salinity effects on plant productivity and soil organic matter decomposition to explore carbon dynamics in TFFW in response to drought-induced saltwater intrusion. Eight sites along the floodplains of the Waccamaw River (USA) and the Savannah River (USA) were selected to represent TFFW transition from healthy to moderately and highly salt-impacted forests, and eventually to oligohaline marshes. TFW-DNDC was calibrated and validated using field observed annual litterfall, stem growth, root growth, soil heterotrophic respiration and soil organic carbon storage. Analyses indicate that plant productivity and soil carbon sequestration in TFFW could change substantially in response to increased soil porewater salinity and reduced soil water table due to drought, but in interactive ways dependent on the river simulated. Such responses are variable due to non-linear relationships between carbon cycling processes and environmental drivers. Plant productivity, plant respiration, soil organic carbon sequestration rate and storage in the highly salt-impacted forest sites decreased significantly under drought conditions compared to normal conditions. Considering the high likelihood of healthy and moderately salt-impacted forests becoming highly salt-impacted forests under future climate change and sea-level rise, it is very likely that TFFW will lose their capacity as carbon sinks without up-slope migration.
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http://dx.doi.org/10.1002/eap.2700DOI Listing
June 2022

Spop ameliorates diabetic nephropathy through restraining NLRP3 inflammasome.

Biochem Biophys Res Commun 2022 02 6;594:131-138. Epub 2022 Jan 6.

Department of Endocrinology, The Second Affiliated Hospital of Xingtai Medical College, No.618 Gangtie North Road, Xindu District, Xingtai, 054000, Hebei, China. Electronic address:

Diabetic nephropathy (DN) is one of the most common causes for end-stage renal disease without effective therapies available. NLR family, pyrin domain-containing 3 (NLRP3) inflammasome possesses a fundamental effect to facilitate the pathogenesis of DN. Unfortunately, how NLRP3 inflammasome is mediated still remains largely unclear. In the present study, an E3 ubiquitin ligase Speckle-type BTB-POZ protein (Spop) was identified as a suppressor of NLRP3 inflammasome. We first showed that Spop expression was extensively down-regulated in kidney of DN patients, which was confirmed in kidney of streptozotocin (STZ)-challenged mice and in high glucose (HG)-stimulated podocytes. Intriguingly, we showed that conditional knockout (cKO) of Spop in podocytes considerably accelerated renal dysfunction and pathological changes in the glomerulus of STZ-induced mice with DN, along with severe podocyte injury. Furthermore, Spop specific ablation in podocytes dramatically facilitated inflammatory response in glomeruli of DN mice via enhancing NLRP3 inflammasome and nuclear factor κB (NF-κB) signaling pathways, which were confirmed in HG-cultured podocytes. Notably, our findings indicated that Spop directly interacted with NLRP3. More importantly, Spop promoted NLRP3 degradation via elevating K48-linked polyubiquitination of NLRP3. Collectively, our findings disclosed a mechanisms through which Spop limited NLRP3 inflammasome under HG condition, and illustrated that Spop may be a novel therapeutic target to suppress NLRP3 inflammasome, contributing to the DN management.
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http://dx.doi.org/10.1016/j.bbrc.2021.12.068DOI Listing
February 2022

Coarse Woody Debris Decomposition Assessment Tool: Model validation and application.

PLoS One 2021 9;16(7):e0254408. Epub 2021 Jul 9.

Northern Research Station, USDA Forest Service, Madison, WI, United States of America.

Coarse woody debris (CWD) is a significant component of the forest biomass pool; hence a model is warranted to predict CWD decomposition and its role in forest carbon (C) and nutrient cycling under varying management and climatic conditions. A process-based model, CWDDAT (Coarse Woody Debris Decomposition Assessment Tool) was calibrated and validated using data from the FACE (Free Air Carbon Dioxide Enrichment) Wood Decomposition Experiment utilizing pine (Pinus taeda), aspen (Populous tremuloides) and birch (Betula papyrifera) on nine Experimental Forests (EF) covering a range of climate, hydrology, and soil conditions across the continental USA. The model predictions were evaluated against measured FACE log mass loss over 6 years. Four widely applied metrics of model performance demonstrated that the CWDDAT model can accurately predict CWD decomposition. The R2 (squared Pearson's correlation coefficient) between the simulation and measurement was 0.80 for the model calibration and 0.82 for the model validation (P<0.01). The predicted mean mass loss from all logs was 5.4% lower than the measured mass loss and 1.4% lower than the calculated loss. The model was also used to assess the decomposition of mixed pine-hardwood CWD produced by Hurricane Hugo in 1989 on the Santee Experimental Forest in South Carolina, USA. The simulation reflected rapid CWD decomposition of the forest in this subtropical setting. The predicted dissolved organic carbon (DOC) derived from the CWD decomposition and incorporated into the mineral soil averaged 1.01 g C m-2 y-1 over the 30 years. The main agents for CWD mass loss were fungi (72.0%) and termites (24.5%), the remainder was attributed to a mix of other wood decomposers. These findings demonstrate the applicability of CWDDAT for large-scale assessments of CWD dynamics, and fine-scale considerations regarding the fate of CWD carbon.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0254408PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8270427PMC
November 2021

Coarse woody debris decomposition assessment tool: Model development and sensitivity analysis.

PLoS One 2021 4;16(6):e0251893. Epub 2021 Jun 4.

Northern Research Station, USDA Forest Service, Madison, Wisconsin, United States of America.

Coarse woody debris (CWD) is an important component in forests, hosting a variety of organisms that have critical roles in nutrient cycling and carbon (C) storage. We developed a process-based model using literature, field observations, and expert knowledge to assess woody debris decomposition in forests and the movement of wood C into the soil and atmosphere. The sensitivity analysis was conducted against the primary ecological drivers (wood properties and ambient conditions) used as model inputs. The analysis used eighty-nine climate datasets from North America, from tropical (14.2° N) to boreal (65.0° N) zones, with large ranges in annual mean temperature (26.5°C in tropical to -11.8°C in boreal), annual precipitation (6,143 to 181 mm), annual snowfall (0 to 612 kg m-2), and altitude (3 to 2,824 m above mean see level). The sensitivity analysis showed that CWD decomposition was strongly affected by climate, geographical location and altitude, which together regulate the activity of both microbial and invertebrate wood-decomposers. CWD decomposition rate increased with increments in temperature and precipitation, but decreased with increases in latitude and altitude. CWD decomposition was also sensitive to wood size, density, position (standing vs downed), and tree species. The sensitivity analysis showed that fungi are the most important decomposers of woody debris, accounting for over 50% mass loss in nearly all climatic zones in North America. The model includes invertebrate decomposers, focusing mostly on termites, which can have an important role in CWD decomposition in tropical and some subtropical regions. The role of termites in woody debris decomposition varied widely, between 0 and 40%, from temperate areas to tropical regions. Woody debris decomposition rates simulated for eighty-nine locations in North America were within the published range of woody debris decomposition rates for regions in northern hemisphere from 1.6° N to 68.3° N and in Australia.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0251893PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8177548PMC
October 2021

Development of Radio-Frequency Sensor Wake-Up with Unmanned Aerial Vehicles as an Aerial Gateway.

Sensors (Basel) 2019 Mar 1;19(5). Epub 2019 Mar 1.

School of Computing and Engineering, University of Missouri-Kansas City, Kansas City, MO 64110, USA.

The advent of autonomous navigation, positioning, and general robotics technologies has enabled the improvement of small to miniature-sized unmanned aerial vehicles (UAVs, or 'drones') and their wide uses in engineering practice. Recent research endeavors further envision a systematic integration of aerial drones and traditional contact-based or ground-based sensors, leading to an aerial⁻ground wireless sensor network (AG-WSN), in which the UAV serves as both a gateway besides and a remote sensing platform. This paper serves two goals. First, we will review the recent development in architecture, design, and algorithms related to UAVs as a gateway and particularly illustrate its nature in realizing an opportunistic sensing network. Second, recognizing the opportunistic sensing need, we further aim to focus on achieving energy efficiency through developing an active radio frequency (RF)-based wake-up mechanism for aerial⁻ground data transmission. To prove the effectiveness of energy efficiency, several sensor wake-up solutions are physically implemented and evaluated. The results show that the RF-based wake-up mechanism can potentially save more than 98.4% of the energy that the traditional duty-cycle method would otherwise consume, and 96.8% if an infrared-receiver method is used.
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http://dx.doi.org/10.3390/s19051047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6427437PMC
March 2019

Impacts of land use, restoration, and climate change on tropical peat carbon stocks in the twenty-first century: implications for climate mitigation.

Mitig Adapt Strateg Glob Chang 2017 13;22(7):1041-1061. Epub 2016 May 13.

3Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR USA.

The climate mitigation potential of tropical peatlands has gained increased attention as Southeast Asian peatlands are being deforested, drained and burned at very high rates, causing globally significant carbon dioxide (CO) emissions to the atmosphere. We used a process-based dynamic tropical peatland model to explore peat carbon (C) dynamics of several management scenarios within the context of simulated twenty-first century climate change. Simulations of all scenarios with land use, including restoration, indicated net C losses over the twenty-first century ranging from 10 to 100 % of pre-disturbance values. Fire can be the dominant C-loss pathway, particularly in the drier climate scenario we tested. Simulated 100 years of oil palm () cultivation with an initial prescribed burn resulted in 2400-3000 Mg CO ha total emissions. Simulated restoration following one 25-year oil palm rotation reduced total emissions to 440-1200 Mg CO ha, depending on climate. These results suggest that even under a very optimistic scenario of hydrological and forest restoration and the wettest climate regime, only about one third of the peat C lost to the atmosphere from 25 years of oil palm cultivation can be recovered in the following 75 years if the site is restored. Emissions from a simulated land degradation scenario were most sensitive to climate, with total emissions ranging from 230 to 10,600 Mg CO ha over 100 years for the wettest and driest dry season scenarios, respectively. The large difference was driven by increased fire probability. Therefore, peat fire suppression is an effective management tool to maintain tropical peatland C stocks in the near term and should be a high priority for climate mitigation efforts. In total, we estimate emissions from current cleared peatlands and peatlands converted to oil palm in Southeast Asia to be 8.7 Gt CO over 100 years with a moderate twenty-first century climate. These emissions could be minimized by effective fire suppression and hydrological restoration.
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http://dx.doi.org/10.1007/s11027-016-9712-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6054005PMC
May 2016

Steric and Stereochemical Modulation in Pyridyl- and Quinolyl-Containing Ligands.

Authors:
Zhaohua Dai

Molecules 2016 Dec 1;21(12). Epub 2016 Dec 1.

Department of Chemistry and Physical Sciences, Forensic Science Program, Pace University, 1 Pace Plaza, New York, NY 10038, USA.

Nitrogen-containing pyridine and quinoline are outstanding platforms on which excellent ionophores and sensors for metal ions can be built. Steric and stereochemical effects can be used to modulate the affinity and selectivity of such ligands toward different metal ions on the coordination chemistry front. On the signal transduction front, such effects can also be used to modulate optical responses of these ligands in metal sensing systems. In this review, steric modulation of achiral ligands and stereochemical modulation in chiral ligands, especially ionophores and sensors for zinc, copper, silver, and mercury, are examined using published structural and spectral data. Although it might be more challenging to construct chiral ligands than achiral ones, isotropic and anisotropic absorption signals from a single chiroptical fluorescent sensor provide not only detection but also differentiation of multiple analytes with high selectivity.
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http://dx.doi.org/10.3390/molecules21121647DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6274402PMC
December 2016

Chiroptical switches: applications in sensing and catalysis.

Molecules 2012 Jan 31;17(2):1247-77. Epub 2012 Jan 31.

Department of Chemistry and Physical Sciences, Pace University, 1 Pace Plaza, New York, NY 10038, USA.

Chiroptical switches have found application in the detection of a multitude of different analytes with a high level of sensitivity and in asymmetric catalysis to offer switchable stereoselectivity. A wide range of scaffolds have been employed that respond to metals, small molecules, anions and other analytes. Not only have chiroptical systems been used to detect the presence of analytes, but also other properties such as oxidation state and other physical phenomena that influence helicity and conformation of molecules and materials. Moreover, the tunable responses of many such chiroptical switches enable them to be used in the controlled production of either enantiomer or diastereomer at will in many important organic reactions from a single chiral catalyst through selective use of a low-cost inducer: Co-catalysts (guests), metal ions, counter ions or anions, redox agents or electrochemical potential, solvents, mechanical forces, temperature or electromagnetic radiation.
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http://dx.doi.org/10.3390/molecules17021247DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6268225PMC
January 2012

Multimode selective detection of mercury by chiroptical fluorescent sensors based on methionine/cysteine.

Chirality 2011 Nov 21;23(10):916-20. Epub 2011 Sep 21.

Department of Chemistry and Physical Sciences, Pace University, New York, New York.

Two multimode Hg(II) sensors, L-MethBQA and L-CysBQA, were obtained by fusing methionine or S-methyl cysteine, into a bis-quinolyl amine-based chiral podand scaffold. Quinolyl groups serve as the fluorophore and possess nitrogen lone pairs capable of chelating metal ions. On exposure to Hg(2+) or Zn(2+), these sensors show signal enhancement in fluorescence. However, Cu(2+) quenches their fluorescence in 30:70 acetontrile/water. L-CysBQA complexes with Hg(2+), producing an exciton-coupled circular dichroism spectrum with the opposite sign to the one that is produced by Cu(2+) or Zn(2+) complexation. L-CysBQA binds Hg(2+) more strongly than Zn(2+) and is shown to differentiate Hg(2+) from other metal ions, such as Zn(2+), Cu(2+), Ni(2+), and Pb(2+), exceptionally well. The synergistic use of relatively soft sulfur, quinoline-based chiral ligands and chiroptically enhanced fluorescence detection results in high sensitivity and selectivity for Hg(2+).
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http://dx.doi.org/10.1002/chir.21015DOI Listing
November 2011

Exploring the scope of redox-triggered chiroptical switches: syntheses, X-ray structures, and circular dichroism of cobalt and nickel complexes of N,N-bis(arylmethyl)methionine derivatives.

Chirality 2008 Mar;20(3-4):585-91

Department of Chemistry, New York University, New York, New York 10003, USA.

N,N-Bis(arylmethyl)methionine derivatives are chiral ligands whose complexes with metal ions may show molecular helicity that can be modulated by defined structural processes. It was shown previously that exciton-coupled circular dichroism (ECCD) spectral amplitude could be modulated by one-electron copper redox chemistry in copper complexes of these ligands. Here we describe the further development of novel systems that show conformational changes resulting in the inversion of exciton chirality. The phenomenon was probed in a N,N-bis(arylmethyl)methionine derivative containing quinoline/pyridine moieties and a methionine carboxylate moiety. The sign of the ECCD of the complex formed between this ligand and CoCl2 is negative, which suggests that the deprotonated carboxylate oxygen coordinates to the metal, but the sulfur atom does not. The sign of the ECCD inverts to positive upon addition of ascorbic acid, which can be turned back to negative upon further treatment with persulfate. X-ray quality crystals of three cobalt complexes and one nickel complex were obtained. The ascorbate-treated cobalt complex of the ligand and the same ligand with nickel, however, vary from the behavior expected from their X-ray crystal structures. It is clear that the solution and crystallographic structures of these complexes differ in several cases.
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http://dx.doi.org/10.1002/chir.20519DOI Listing
March 2008

Visual snapshots of intracellular kinase activity at the onset of mitosis.

Chem Biol 2007 Nov;14(11):1254-60

Department of Biochemistry, The Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY 10461, USA.

Visual snapshots of intracellular kinase activity can be acquired with exquisite temporal control by using a light-activatable (caged) sensor, thereby providing a means to interrogate enzymatic activity at any point during the cell-division cycle. Robust protein kinase activity transpires just prior to, but not immediately after, nuclear envelope breakdown (NEB). Furthermore, kinase activity is required for the progression from prophase into metaphase. Finally, the application of selective protein kinase C (PKC) inhibitors, in combination with the caged sensor, correlates the action of the PKC beta isoform with subsequent NEB.
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http://dx.doi.org/10.1016/j.chembiol.2007.10.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2171364PMC
November 2007

Light-regulated sampling of protein tyrosine kinase activity.

J Am Chem Soc 2006 Nov;128(43):14016-7

Department of Biochemistry, The Albert Einstein College of Medicine of Yeshiva University, 1300 Morris Park Avenue, Bronx, NY 10461, USA.

Protein tyrosine kinases serve as key mediators of signaling pathways, biochemical highways that control various aspects of cell behavior. Although fluorescent reporters of tyrosine kinases have been described, these species can suffer immediate phosphorylation upon exposure to the cellular milieu, thereby hindering a detailed analysis of kinase activity as a function of the cell cycle or exposure to environmental stimuli. The first example of a light-regulated tyrosine kinase reporter is described herein, which allows the investigator to control when kinase activity is sampled. In addition, the set of sensors created in this study contain different fluorophores, each with its own unique photophysical properties, thereby furnishing an array of choices that can be used in combination with other intracellular probes.
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http://dx.doi.org/10.1021/ja065852zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2660521PMC
November 2006

Rigidified tripodal chiral ligands in the asymmetric recognition of amino compounds.

Chirality 2005 ;17 Suppl:S227-33

Department of Chemistry, New York University, New York, New York 10003, USA.

Chiral rigidified piperidine and quinuclidine analogues of tris(2-pyridylmethyl)amine (TPA) derivatives were examined for asymmetric recognition of amino compounds by cyclic voltammetry and fluorescence. A Cu(II) complex of a piperidine analogue discriminated the enantiomers of some chiral amines and amino alcohols, giving differences in electrochemical potential for diastereomeric complexes. Protonated piperidine and quinuclidine analogues were able to differentiate the two enantiomers of certain amino alcohols by fluorescence spectroscopy. The quinuclidine analogue gave a 3-fold difference in response to the two enantiomers of phenyglycinol.
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http://dx.doi.org/10.1002/chir.20130DOI Listing
September 2005

Ratiometric displacement approach to Cu(II) sensing by fluorescence.

J Am Chem Soc 2005 Feb;127(6):1612-3

Department of Chemistry, New York University, New York, NY 10003, USA.

A chelation-enhanced fluorescence method for the detection of paramagnetic copper(II) ions is developed. Two dyes with unequal metal ion binding constants are used, each giving strong fluorescence enhancement in the presence of a diamagnetic reporter ion such as cadmium(II). Upon presentation of copper(II) to a 1:1:1 mixture of the two dyes and cadmium(II), the Cd(II) is displaced from one dye to the other, resulting in quenching of one dye by the Cu(II) and enhancement of the weaker binding dye by complexation of the Cd(II). Although several criteria must be met, this method holds promise for analysis of a wide range of analytes.
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http://dx.doi.org/10.1021/ja0431051DOI Listing
February 2005

Detection of zinc ions by differential circularly polarized fluorescence excitation.

J Am Chem Soc 2004 Sep;126(38):11760-1

Department of Chemistry, New York University, New York, New York 10003, USA.

A new chiroptical spectroscopic approach, differential circularly polarized fluorescence excitation (CPE), can be used to provide a selective method for detecting the presence of zinc ions. The approach utilizes the same instrumentation as fluorescence-detected circular dichroism and provides strong contrast in metal detection due to response to both chelation-enhanced fluorescence and circular dichroism upon metal ion binding. The observed contrast is therefore better than either of the parent spectroscopic detection methods. CPE also provides a strategy to reduce interference from background such as protein-based tryptophan fluorescence.
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http://dx.doi.org/10.1021/ja047213zDOI Listing
September 2004

Stereochemical control of Zn(II)/Cu(II) selectivity in piperidine tripod ligands.

Chem Commun (Camb) 2002 Jul(13):1414-5

Department of Chemistry, New York University, New York, NY 10003, USA.

Stereochemistry plays a major role in the selectivity toward zinc ion over copper(II) of some tripodal ligands with a central piperidine scaffold, one of which acts as a fluorescent zinc sensor with nanomolar sensitivity.
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http://dx.doi.org/10.1039/b111259gDOI Listing
July 2002
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