Biphasic Behavior Research Articles

Kinetic modelling of ligand trapping inside acidic vesicles containing alpha-4 beta-2 nicotinic receptors as an explanation for long-term cessation effect of varenicline (Chantix).

Govind's et. al. 2017 paper proposes that the smoking cessation effect of varenicline (or epibatidine) is caused by these molecules being trapped inside acidic vesicles containing α4β2 nicotinic receptors. These ligands are weak bases with high affinity to these receptors. The trapping would lead to their slower release and longer desensitization of the receptors, thereby reducing nicotine upregulation. Meanwhile, nicotine, with lower pKa and lower binding affinity is not trapped within the vesicles. It is unclear whether the acidity of the vesicles and the presence of receptors is sufficient to explain the biphasic trapping behavior observed empirically. To better understand this phenomenon, we model flux of ligands between cellular compartments using Flick's first law of diffusion and the Nernst-Plank Equation. The ratio of neutral to charged ligands within each compartment is calculated via Henderson-Hasselbach equation. Main parameters in the model include the number of vesicles, receptors per vesicle, ratio of vesicles to non-vesicle receptors, pH, membrane permeability, pKa and dissociation constants of the ligand. The system is solved numerically using MATLAB and optimized against empirical data. The results show the experimentally observed biphasic release of epibatidine, affirming the hypothesis of trapping inside the vesicles. Our model also shows that the main trapping effect is due to the presence of receptors inside vesicles, not those located on the cell surface and the high affinity of these ligands to the receptors. The exact acidity level inside the vesicles is not as important. Our model is also able to predict the much faster nicotine outward flow compared with epibatidine. This model can be used to predict the kinetics of other weak basic ligands like those used in positron emission tomography.

Fabrication, Optimization, and Evaluation of Paclitaxel and Curcumin Coloaded PLGA Nanoparticles for Improved Antitumor Activity.

Codelivery of chemotherapeutic drugs in nanoparticles can enhance the therapeutic effects against tumors. However, their anticancer properties and physiochemical characteristics can be severely influenced by many formulation parameters during the preparation process. It is a complicated development phase to select the optimal parameters for preparation of nanoparticles based on the commonly used one single parameter method, which consumes a lot of money, time, and effort, and sometimes even fails. Therefore, the statistical analysis based on Box-Behnken design (BBD) has attracted much attention in bioengineering fields because it can illustrate the influence of parameters, build mathematical models, and predict the optimal combinational factors in a decreased number of experiments. In this study, we used a three-factor three-level BBD design to optimize the preparation of poly(lactic-co-glycolic acid) (PLGA) nanoparticles coloaded with two anticancer drugs curcumin and paclitaxel (PLGA-CUR-PTX nanoparticles). The surfactant concentration, polymer concentration, and oil-water ratio were selected as independent variables. An optimized model of the formulation for PLGA-CUR-PTX nanoparticles was validated. The optimal nanoparticles possessed a uniform spherical shape, with an average size of 99.94 nm, and the drug encapsulation efficiencies of CUR and PTX were 63.53 and 80.64%, respectively. The drug release from nanoparticles showed a biphasic release behavior, with a release mechanism via diffusion and fundamentally quasi-Fickian diffusion. The optimized nanoparticles demonstrated an enhanced cytotoxicity effect with lower IC50 values to 4T1 and MCF-7 breast cancer cell lines compared to free drugs. In summary, BBD optimization of CUR and PTX coloaded nanoparticles yielded a favorable drug carrier that holds potential as an alternative treatment for anticancer therapy.

Pioglitazone-loaded nanostructured lipid carriers: In-vitro and in-vivo evaluation for improved bioavailability

Pioglitazone (PZ), a highly lipophilic Class II drug with poor aqueous solubility possesses low oral bioavailability. The oral bioavailability of pioglitazone can be improved by incorporating into nanostructured lipid carriers (NLCs). Pioglitazone-loaded nanostructured lipid carriers (PZ-loaded NLCs) were developed by using the solvent emulsification evaporation method. The lipid phase of the formulation consists of a solid and liquid lipid mixture (fatty acids and oils) and surfactants (Tween 20, Span 40) were used for the stability of the formulation. PZ-loaded NLCs were characterized for physicochemical characteristics including particle size, zeta potential, polydispersity index (PDI), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) and stability studies. Moreover, drug entrapment efficiency, drug loading capacity, drug release, toxicity studies, permeation studies, and in-vivo studies were performed to evaluate enhanced bioavailability. PZ-loaded NLCs have shown an average particle size of 152 nm, PDI of 0.19, and a negative value of zeta potential. Drug entrapment efficiency and loading capacity were about 83% and 5.8%, respectively. SEM results delineated the smooth homogenous surface in nano-sized range, whereas FTIR spectra demonstrated no interaction between components of PZ-loaded NLCs formulation. For drug release studies, the dialysis bag method confirmed a biphasic release behavior in beginning followed by slow, controlled release up to 24 h. Furthermore, permeation studies showed enhanced permeability and in-vivo studies confirmed the enhanced bioavailability of pioglitazone. Based on the above finding, it can be concluded that NLCs are a versatile tools for enhancing the bioavailability of poorly soluble Class II drugs.

Unconfined Compression Experimental Protocol for Cartilage Explants and Hydrogel Constructs: From Sample Preparation to Mechanical Characterization.

Mechanical characterization of articular cartilage and cell-seeded hydrogel constructs is a challenging task due to the complex biphasic behavior of these materials. Here we describe a step-by-step unconfined compression testing protocol for inverse mechanical characterization of these materials from sample preparation to parameter identification. Examples from our ongoing experiments on alginate hydrogel constructs and preserved and damaged cartilage explants obtained from human hip samples are presented.

Review of recent trends and various techniques for CO2 capture: Special emphasis on biphasic amine solvents

In the present scenario, the hazardous impacts of greenhouse gases can be restricted by adopting carbon capture and storage (CCS) technology that captures most of the CO2 emitted by numerous industries, human activities, and mostly from thermal power plants. This paper reviewed the main CO2 capturing technologies, i.e., pre-combustion, post-combustion, and oxy-combustion, along with their different operating conditions, performances, and comparisons. Some industrial processes used to capture CO2 by physical solvents are presented with their properties and working conditions. Methodologies like absorption, adsorption, membrane technology, cryogenic separation, and microalgae process are presented. Single alkanolamine-based solvents have limited CO2 loading and high regeneration energy demand, attracting researchers to work on their various amine blends. In today’s scenario, biphasic solvents play a vital role in the field of CO2 capture. Some amine solvent blends show biphasic behavior, leading to faster reaction, higher absorption capacity, and lower regeneration energy. The solvent screening for the biphasic solvent is very rigorous and still challenging. In this work, various blends selected by the researchers with the potential for phase-splitting behavior are reviewed, and the best among them is reported.

Theoretical and experimental study of anomalous Nernst effect in biphasic magnetic system

We perform a theoretical and experimental investigation of magnetic properties and anomalous Nernst effect in a NiFe/Cr/NiFe trilayer. Our system presents a biphasic magnetic behavior, a response owed to distinct structural properties of the bottom and top magnetic layers. We verify the thermomagnetic results strongly depend on the anisotropies and magnetic response of the biphasic system. Moreover, the thermomagnetic results seem to be much more sensitive to the anisotropies than the magnetometry ones. We show the anomalous Nernst coefficient found in our trilayer is quite comparable with those verified for high-efficient thermomagnetic systems. We also disclose an enhancement if compared with the ones observed for single layers. Beyond, our results highlight the role of each ferromagnetic layer on the thermomagnetic response. Our experimental and theoretical findings show that the top and bottom layers contribute differently to the thermomagnetic signal due to the Cr spacer in the trilayer system.

Host and viral proteins involved in SARS-CoV-2 infection differentially bind heme.

In most severe cases, SARS‐CoV‐2‐induced autoimmune reactions have been associated with hemolytic complications. Hemolysis‐derived heme from ruptured red blood cells has been shown to trigger a variety of fatal proinflammatory and procoagulant effects, which might deteriorate the progression of COVID‐19. In addition, the virus itself can induce proinflammatory signals via the accessory protein 7a. Direct heme binding to the SARS‐CoV‐2 protein 7a ectodomain and other COVID‐19‐related proteins has been suggested earlier. Here, we report the experimental analysis of heme binding to the viral proteins spike glycoprotein, protein 7a as well as the host protein ACE2. Thus, protein 7a chemical synthesis was established, including an in‐depth analysis of the three different disulfide‐bonded isomers. Surface plasmon resonance spectroscopy and in silico studies confirm a transient, biphasic binding behavior, and heme‐binding affinities in the nano‐ to low micromolar range. These results confirm the presence of the earlier identified heme‐binding motifs and emphasize the relevance for consideration of labile heme in preexisting or SARS‐CoV‐2‐induced hemolytic conditions in COVID‐19 patients.

Selective serotonin reuptake inhibitors and inflammatory bowel disease; Beneficial or malpractice.

IBD, a chronic inflammatory disease, has been manifested as a growing health problem. No Crohn’s and Colitis councils have officially ratified anti-depressants as a routine regimen for IBD patients. However, some physicians empirically prescribe them to rectify functional bowel consequences such as pain and alleviate psychiatric comorbidities. On the other side, SSRIs’ prescription is accompanied by adverse effects such as sleep disturbances. Prolonged intermittent hypoxia throughout sleep disturbance such as sleep apnea provokes periodic reductions in the partial oxygen pressure gradient in the gut lumen. It promotes gut microbiota to dysbiosis, which induces intestinal inflammation. This phenomenon and evidence representing the higher amount of serotonin associated with Crohn’s disease challenged our previous knowledge. Can SSRIs worsen the IBD course? Evidence answered the question with the claim on anti-inflammatory properties (central and peripheral) of SSRIs and illuminated the other substantial elements (compared to serotonin elevation) responsible for IBD pathogenesis. However, later clinical evidence was not all in favor of the benefits of SSRIs. Hence, in this review, the molecular mechanisms and clinical evidence are scrutinized and integrated to clarify the interfering molecular mechanism justifying both supporting and disproving clinical evidence. Biphasic dose-dependent serotonin behavior accompanying SSRI shifting function when used up for the long-term can be assumed as the parameters leading to IBD patients’ adverse outcomes. Despite more research being needed to elucidate the effect of SSRI consumption in IBD patients, periodic prescriptions of SSRIs at monthly intervals can be recommended.

Functional Nanogel from Natural Substances for Delivery of Doxorubicin

Nanogels (NGs) have attracted great attention because of their outstanding biocompatibility, biodegradability, very low toxicity, flexibility, and softness. NGs are characterized with a low and nonspecific interaction with blood proteins, meaning that they do not induce any immunological responses in the body. Due to these properties, NGs are considered promising candidates for pharmaceutical and biomedical application. In this work, we introduce the development of novel functional nanogel obtained from two naturally based products—citric acid (CA) and pentane-1,2,5-triol (PT). The nanogel was synthesized by precipitation esterification reaction of CA and PT in tetrahydrofuran using N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide (EDC) and 4-(dimethylamino)pyridine (DMAP) catalyst system. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM) analyses revealed formation of spherical nanogel particles with a negative surface charge. Next, the nanogel was loaded with doxorubicin hydrochloride (DOX) by electrostatic interactions between carboxylic groups present in the nanogel and amino groups of DOX. The drug-loaded nanogel exhibited high encapsulation efficiency (EE~95%), and a bi-phasic release behavior. Embedding DOX into nanogel also stabilized the drug against photodegradation. The degradability of nanogel under acidic and neutral conditions with time was investigated as well.

Inhibition of Class I Histone Deacetylase Activity Blocks the Induction of TNFAIP3 Both Directly and Indirectly via the Suppression of Endogenous TNF-α

Histone deacetylase inhibitors (HDIs) are promising drugs for the treatment of inflammatory diseases. However, their therapeutical exploitation is slowed down by severe adverse manifestations that can hardly be foreseen, mainly due to incomplete knowledge of how HDIs impact the delicate balance of inflammatory mediators. In this work, we characterized the effects of the HDI trichostatin A (TSA) on the expression of TNFAIP3, which is a crucial inhibitor of the classical NF-kB pathway and an LPS-induced negative feedback regulator. The accumulation of TNFAIP3 mRNA after LPS stimulation showed biphasic behavior, with one wave within the first hour of stimulation and a second wave several hours later, which were both reduced by TSA. By using inhibition and knockdown approaches, we identified two temporally and mechanistically distinct modes of action. The first wave of TNAIP3 accumulation was directly blunted by the histone deacetylase (HDAC) blockade. By contrast, the second wave was decreased mainly because of the lack of endogenous TNF-α induction, which, in turn, depended on the intact HDAC activity. In both cases, class I HDACs appeared to play a nonredundant role, with HDAC3 required, but not sufficient, for TNF-α and TNFAIP3 induction. In addition to TNFAIP3, TNF-α is known to induce many response genes that orchestrate the inflammatory cascade. Thus, suppression of TNF-α may represent a general mechanism through which HDIs regulate a selected set of target genes.

Verapamil hydrochloride loaded solid lipid nanoparticles: Preparation, optimization, characterisation, and assessment of cardioprotective effect in experimental model of myocardial infarcted rats

Verapamil, a calcium channel blocker has poor bioavailability (20–30%) owing to extensive hepatic first-pass metabolism. Hence, the major objective of this research was to improve the oral bioavailability of Verapamil by Solid Lipid Nanoparticles (V-SLNs) using high shear homogenization and ultrasonication technology. A 32 factorial design was employed to statistically optimize the formulation to get minimum particle size with maximum entrapment efficiency. The average particle size was 218 nm and the entrapment efficiency was 80.32%. The V-SLN formulation exhibited biphasic behavior with a rapid release at first, then a steady release (75–80%) up to 24 h following the Korsmeyer Peppas release model. In the Isoproterenol induced myocardial necrosis model, oral administration of V-SLNs positively modulated almost all the studied hemodynamic parameters such as left ventricular end-diastolic pressure, cardiac injury markers, and tissue architecture. The cardioprotective effect was also confirmed with histopathological studies. When compared with free drugs, in-vivo pharmacokinetic studies demonstrated a rise in t1/2, AUC0-∞, and Cmax, indicating that bioavailability has improved. These encouraging results demonstrate the promising potential of developed V-SLNs for oral delivery and thereby improve the therapeutic outcome.

Design and optimization of gatifloxacin loaded polyvinyl alcohol nanofiber for the treatment of dry eye infection: In vitro and in vivo evaluation

According to a clinical report, nearly 50% of dry eye patients have an elevated risk of ocular infections and inflammations. Nanofiber could serve as a potential vehicle for treating anterior ocular disease because of its sterile nature, known solubility enhancing ability, capacity to carry multiple drugs, and controlled drug release capability, which can minimize overall dose and dosing frequency. As a result, the goal of this study was to assess the therapeutic potential of Gatifloxacin (GAF) loaded Polyvinyl alcohol (PVA) nanofiber for the treatment of dry eye syndrome with infection. Towards in vitro assessment, optimized nanofiber was characterized through surface imaging, swelling, release behavior, sterility, residual solvent, and degradation studies. Goat cornea was used to determine trans corneal penetrability. Therapeutic performance of the optimized nanofibers was assessed in a dry eye animal model. Results showed that applied potential of 12 kV, the flow rate of 3 μl/min, and plate to collector distance of 20 cm were the optimized electrospinning parameters for bead-free uniform fiber of around 200 nm. Longer precorneal contact time and biphasic release behavior, with an initial burst phase followed by a 7-h controlled release profile, are thought to reduce the need for frequent dosing to manage dry eye issues. Additionally, there was partial tear volume restitution and the tear ferns revival after 36h. Overall, the in-vitro and in-vivo results suggested that the developed product could be a viable alternative to manage dry eye infectious syndrome with less frequent dosing.

Transparent exopolymer particles-associated membrane fouling analyses of systems containing sodium alginate, calcium, iron, alum and their combination during dead-end ultrafiltration

In this work, a serious of filtration experiments were designed and implemented to compare the effects of different metal cations (Ca2+, Fe3+, and Al3+) on fouling by sodium alginate. As indicated by the experimental results, these three types of cations all induced biphasic filtration behavior by 50 mg/L sodium alginate, that addition of these cations initially aggravated the fouling but then mitigated it upon further addition. The maximum specific filtration resistance (αav) increased in the following order: Al (34.5 ± 1.2 1014 mg/kg) < Ca (52.4 ± 2.5 1014 mg/kg) ≈Fe (54.1 ± 1.2 1014 mg/kg), but the corresponding critical concentration of the cation was in the order: Al3+ (0.02 mM) = Fe3+ (0.02 mM) < Ca2+ (0.05 mM). Increasing the metal cation concentration induced a higher transparent exopolymer particle concentration with the size being initially decreased but then gradually increased via the cation bridging effect, until the cation concentration reached up to 2 mM with the formation of metal hydroxides. So the fouling resistance mainly resulted from the dynamic equilibrium between concentrations and properties of transparent exopolymer particles with different sizes (0.05–0.1 μm, 0.1–0.2 μm, 0.2–0.4 μm and >0.4 μm). Similar biphasic fouling behavior also observed in the co-existence of Ca2+ and Fe3+/Al3+, but the comparable maximum αav values were obtained at much lower ion concentrations. Besides changes in the transparent exopolymer particle concentration, the hindered back transport of different sodium alginate molecules and steric effect also contributed to the synergistic fouling. Furthermore, there was little competition between the binding sites for divalent and trivalent ions, but the coiling behavior could be limited by changing the cation dosing sequence, leading to a weakened synergistic effect. This study links cation types, transparent exopolymer particle formations and fouling layer structures, with practical relevance for the hydraulic performance of low-pressure membranes, hopefully leading to their wider application in water treatment.

Analgesic effect of gastrin-releasing peptide in the dorsal horn

Itch and pain are both unpleasant, but they are discrete sensations. Both of these sensations are transmitted by C-fibers and processed in laminae I-II of the dorsal horn. To examine whether pruriception modulates pain, we first confirmed the activation of cells in the itch-related circuits that were positive for gastrin-releasing peptide (GRP) and GRP receptor (GRPR) using a paw formalin injection model. This pain model with typical biphasic pain behavior increased c-Fos but did not affect the expressions of GRP and GRPR mRNAs in the dorsal horn. Using c-Fos expression as a marker for activated cells, we confirmed that formalin injection increased the number of cells double-labeled for c-Fos and GRP or GRPR in the dorsal horn. The emergence of these neurons indicates the activation of itch-related circuits by acute pain signals. The effect of an antagonist for a GRPR was examined in the paw formalin injection model. Intrathecal chronic antagonization of spinal GRPR enhanced the onset of phase II of paw formalin injection-induced pain behavior. Exogenous intrathecal GRP infusion to the paw-formalin injection model not only showed significant reduction of pain behavior but also increased c-Fos in the inhibitory neurons in the dorsal horn. The anti-nociceptive effect of spinal GRP infusion was observed in the peripheral inflammation model (complete Freund’s adjuvant injection model). In this study we suggest that painful stimuli activated itch-related neuronal circuits and uncovered the spinal activation of the itch-induced analgesic effect on acute and established inflammatory pain.

Multiscale modelling for investigating the long-term time-dependent biphasic behaviour of the articular cartilage in the natural hip joint.

A better understanding of the time-dependent biomechanical behaviour of the biphasic hip articular cartilage (AC) under physiological loadings is important to understand the onset of joint pathology and guide the clinical treatment. Current computational studies for the biphasic hip AC were usually limited to short-term duration or using elaborate loading. The present study aimed to develop a multiscale computational modelling to investigate the long-term biphasic behaviour of the hip AC under physiological loadings over multiple gait cycles. Two-scale computational modelling including a musculoskeletal model and a finite element model of the natural hip was created. These two models were then combined and used to investigate the biphasic behaviour of hip AC over 80 gait cycles. The results showed that the interstitial fluid pressure in the AC supported over 89% of the loading during gait. When the contact area was located at the AC centre, the contact pressure and fluid pressure increased over time from the first cycle to the 80th cycle, while when the contact area approached the edge, these pressures decreased first dramatically and then slowly over time. The peak stresses and strains in the solid matrix of the AC remained at a low level and increased over time from the first cycle to the 80th cycle. This study demonstrated that the long-term temporal variations of the biphasic behaviour of hip AC under physiological loadings are significant. The methodology has potentially important implications in the biomechanical studies of human cartilage and supporting the development of cartilage substitution.

Artificial Biphasic Synapses Based on Nonvolatile Phase‐Change Photonic Memory Cells

Nonvolatile photonic memory cells are basic building blocks for neuromorphic hardware enabling the realization of all‐optical synapses and artificial neurons. These devices commonly exploit chalcogenide phase‐change materials, which are evanescently coupled to photonic waveguides, and provide fast write/erase speeds and large storage capacity. Here, we report for the first time the programming of a nonvolatile photonic memory cell based on Ag3In4Sb76Te17 (AIST) which is capable of mimicking biphasic synapses. We evaluate the underlying mechanism of biphasic behavior of AIST cells based on numerical simulations and correlate to experimental findings. Switching dynamics demonstrate enhanced performance with a post‐excitation dead time as short as 12.8 ns. Based on AIST double cells, we demonstrate reversible multilevel switching between 45 unique synaptic weights for long‐term depression (LTD) and long‐term potentiation (LTP). The observed biphasic programming and excellent switching performance render AIST‐based photonic memory cells promising for artificial neural networks and neuromorphic photonic computing hardware.

Finite element investigations of the fluid-solid behaviour in a bio-inspired poroelastic bearing

Poroelastic materials are commonly found in biological systems, such as articulating cartilage, and the ability to predict their biphasic behaviour is a key step in the understanding of joint health and the development of biomimetic devices. Here, a fully coupled three dimensional finite element study is presented to demonstrate the permeability dependent load carrying capacity of fluid pressure in a time-varying poroelastic system. A bio-inspired material model is demonstrated with relaxation simulations which first show results for a cartilage-like sample and then for a variation of permeability from [Formula: see text] to [Formula: see text]. The relaxation rate is non-linear but the total relaxation time scales linearly with permeability. That material model is then demonstrated in the context of a mechanical bearing operating in lubricated contact with an impermeable wall. The results show that for a given set of operating conditions the permeability modifies how the fluid and solid phases accommodate applied loads. High fluid load support varies through the thickness and width of the bearing. It is particularly high around regions where the interstitial flow is restricted by external factors such as contact interfaces. The model offers a novel method to predict local pressures and stresses within a poroelastic material.

Pharmacokinetics of metamizole (dipyrone) as an add-on in calves undergoing umbilical surgery.

This preliminary clinical investigation of the pharmacokinetic behavior of the main metamizole (dipyrone) metabolites 4-methylaminoantipyrine (4-MAA) and 4-aminoantipyrine (4-AA) in calves undergoing umbilical surgery is part of an already published main study. A single intravenous dose of metamizole was added to ketamine/xylazine/isoflurane anesthesia. Eight Simmental calves weighing 90 ± 10.8 kg and aged 47.6 ± 10.4 days received 40 mg/kg metamizole intravenously 10 minutes prior to general anesthesia. Blood samples were collected over 24 hours and analyzed for 4-MAA and 4-AA. Meloxicam was additionally given twice: 2.5 hours pre- and 20.5 hours postsurgically. The pharmacokinetic profile of 4-MAA was best fitted to a two-compartment model and was characterized by a fast distribution half-life and slow elimination half-life (t½alpha = 5.29 minutes, t½beta = 9.49 hours). The maximum concentration (Cmax 101.63 μg/mL) was detected at the first measurement time point 15 minutes after administration. In contrast, 4-AA showed fast, high and biphasic plasma peak concentration behavior in five calves (2.54-2.66 μg/mL after 15-30 minutes, and 2.10-2.14 μg/mL after 2-3.5 hours) with a t½beta of 8.87 hours, indicating a rapid distribution and subsequent redistribution from well-perfused organs. Alternatively, three calves exhibited a slower and lower monophasic plasma peak concentration (1.66 μg/mL after 6.5 hours) with a t½beta of 6.23 hours, indicating slow accumulation in the intravascular compartment. The maximum concentration and area under the plasma concentration curve (AUC) of 4-AA were lower than those of 4-MAA. This metabolic behavior supports our already published data on clinical monitoring and plasma cortisol concentrations (PCCs). Compared to those of saline controls, lower PCCs correspond to the t½alpha of 4-MAA. Data on Tmax and t½beta also match these clinical observations. However, further studies are required to assess the exact analgesic mechanism and potency of the metamizole metabolites in calves.

Sulfur Stable Isotope Discrimination in Rice: A Sulfur Isotope Mass Balance Study.

The use of sulfur (S) stable isotopes to study S metabolism in plants is still limited by the relatively small number of studies. It is generally accepted that less S stable isotope discrimination occurs during sulfate (SO42–) uptake. However, S metabolism and allocation are expected to produce separations of S stable isotopes among the different plant S pools and organs. In this study, we measured the S isotope composition of the main S pools of rice plants grown under different SO42– availabilities in appropriate closed and open hydroponic-plant systems. The main results indicate that fractionation against 34S occurred during SO42– uptake. Fractionation was dependent on the amount of residual SO42– in the solution, showing a biphasic behavior related to the relative expression of two SO42– transporter genes (OsSULTR1;1 and OsSULTR1;2) in the roots. S isotope separations among S pools and organs were also observed as the result of substantial S isotope fractionations and mixing effects occurring during SO42– assimilation and plant S partitioning. Since the S stable isotope separations conserve the memory of the physiological and metabolic activities that determined them, we here underline the potential of the 32S/34S analysis for the detailed characterization of the metabolic and molecular processes involved in plant S nutrition and homeostasis.

A detailed investigation to study the pattern of the interplay of Cyclic AMP Receptor Protein (CRP) of E. coli with its different classes of promoters

The activity of most of the promoters in Escherichia coli, involved in the metabolism of sugars other than glucose, is controlled by a CRP (cAMP receptor protein) or CAP (catabolite activator protein). CRP-dependent promoters are differentiated into various classes (Class I, Class II, and Class III) based on its cognate binding site’s position on DNA. The promoters regulated by CAP are differentially regulated by this transcriptional factor and it is also imperative to mention that these promoters vary greatly in respect to the binding site of CAP to its cognate binding site, it has also been reported that either it overlaps with the binding site of RNA polymerase or it present upstream to it. In Class I CAP-dependent promoters, a particular CAP molecule makes protein-protein interaction for the start of transcription. In Class II CAP-dependent promoters, a particular CAP molecule makes multiple interactions for the start of transcription. At last, in Class III-CAP dependent promoters, more than one CAP molecule is involved and activation of transcription is done synergistically. It has also been documented that CAP shows a kind of biphasic behavior in some promoters. So, the main focus of this work is to find out whether this biphasic behavior is true for other E. coli promoters as well. Experiments have been performed to know more about this biphasic nature and the various patterns of interactions of catabolite activator protein (CAP) of E. coli with its different classes of promoters.