Estimation of the proximal temperature rise of an excited upconversion particle by detecting the wavefront of emission.

Monitoring the temperature distribution within a local environment at the micro and nanoscale is vital as many processes are solely thermal. Various thermometric techniques have been explored in the community, and out of these, fluorescent nano/micro particle-based mechanisms are accepted widely (fluorescence intensity ratio (FIR) techniques, where the ratio of populations in two consecutive energy levels is compared with Boltzmann distribution). We describe a new technique to account for the temperature rise near an illuminated upconverting particle (UCP) using wavefront imaging, which is more sensitive than the conventional thermometric techniques on the microscale. We rely on a thermo-optical phase microscopic technique by reconstructing the wavefront of emission from an upconverting particle using a Shack-Hartmann wavefront sensor. The wavefront maps the local phase distribution, which is an indicator of the surroundings' optical parameters, particularly the suspended medium's temperature-induced refractive index in the presence of convection currents. We describe how these extracted phase values can provide information about the optical heating due to the particle and hence its local environment along the direction of the emission. Our findings demonstrate the detection of a minimum temperature rise of 0.23 K, while the FIR methods indicate a minimum of 0.3 K rise. This technique is used to study the temperature increase in the backscattered direction for an upconverting particle illuminated on pump resonance. We also estimate the Soret coefficient for an upconverting particle optically trapped on pump resonance and experiencing anisotropic heating across the body.

Lean blowout detection using topological data analysis.

Modern lean premixed combustors are operated in ultra-lean mode to conform to strict emission norms. However, this causes the combustors to become prone to lean blowout (LBO). Online monitoring of combustion dynamics may help to avoid LBO and help the combustor run more safely and reliably. Previous studies have suggested various techniques to early predict LBO in single-burner combustors. In contrast, early detection of LBO in multi-burner combustors has been little explored to date. Recent studies have discovered significantly different combustion dynamics between multi-burner combustors and single-burner combustors. In the present paper, we show that some well-established early LBO detection techniques suitable for single-burner combustor are less effective in early detecting LBO in multi-burner combustors. To resolve this, we propose a novel tool, topological data analysis (TDA), for real-time LBO prediction in a wide range of combustor configurations. We find that the TDA metrics are computationally cheap and follow monotonic trends during the transition to LBO. This indicates that the TDA metrics can be used to fine-tune the LBO safety margin, which is a desirable feature from practical implementation point of view. Furthermore, we show that the sublevel set TDA metrics show approximately monotonic changes during the transition to LBO even with low sampling-rate signals. Sublevel set TDA is computationally inexpensive and does not require phase-space embedding. Therefore, TDA can potentially be used for real-time monitoring of combustor dynamics with simple, low-cost, and low sampling-rate sensors.

Pigments from pathogenic bacteria: a comprehensive update on recent advances.

Bacterial pigments stand out as exceptional natural bioactive compounds with versatile functionalities. The pigments represent molecules from distinct chemical categories including terpenes, terpenoids, carotenoids, pyridine, pyrrole, indole, and phenazines, which are synthesized by diverse groups of bacteria. Their spectrum of physiological activities encompasses bioactive potentials that often confer fitness advantages to facilitate the survival of bacteria amid challenging environmental conditions. A large proportion of such pigments are produced by bacterial pathogens mostly as secondary metabolites. Their multifaceted properties augment potential applications in biomedical, food, pharmaceutical, textile, paint industries, bioremediation, and in biosensor development. Apart from possessing a less detrimental impact on health with environmentally beneficial attributes, tractable and scalable production strategies render bacterial pigments a sustainable option for novel biotechnological exploration for untapped discoveries. The review offers a comprehensive account of physiological role of pigments from bacterial pathogens, production strategies, and potential applications in various biomedical and biotechnological fields. Alongside, the prospect of combining bacterial pigment research with cutting-edge approaches like nanotechnology has been discussed to highlight future endeavours.

In silico evolutionary and structural analysis of cAMP response proteins (CARPs) from Leishmania major.

With unidentified chemical triggers and novel-effectors, cAMP signaling is broadly noncanonical in kinetoplastida parasites. Though novel protein kinase A regulatory subunits (PKAR) have been identified earlier, cAMP Response Proteins (CARPs) have been identified as a unique and definite cAMP effector of trypanosomatids. CARP1-CARP4 emerged as critical regulatory components of cAMP signaling pathway in Trypanosoma with evidences that CARP3 can directly interact with a flagellar adenylate cyclase (AC). CARP-mediated regulations, identified so far, reflects the mechanistic diversity of cAMP signaling. Albeit the function of the orthologous is not yet delineated, in kinetoplastids like Leishmania, presence of CARP1, 2 and 4 orthologues suggests existence of conserved effector mechanisms. Targeting CARP orthologues in Leishmania, a comprehensive evolutionary analysis of CARPs have been aimed in this study which revealed phylogenetic relationship, codon adaptation and structural heterogeneity among the orthologues, warranting functional analysis in future to explore their involvement in infectivity.

A comprehensive profiling of quorum quenching by bacterial pigments identifies quorum sensing inhibition and antibiofilm action of prodigiosin against Acinetobacter baumannii.

Bacterial pigments represent a diverse group of secondary metabolites, which confer fitness advantages to the producers while residing in communities. The bioactive potential of such metabolites, including antimicrobial, anticancer, and immunomodulation, are being explored. Reckoning that a majority of such pigments are produced in response to quorum sensing (QS) mediated expression of biosynthetic gene clusters and, in turn, influence cell-cell communication, systemic profiling of the pigments for possible impact on QS appears crucial. A systemic screening of bacterial pigments for QS-inhibition combined with exploration of antibiofilm and antimicrobial action against Acinetobacter baumannii might offer viable alternatives to combat the priority pathogen. Major bacterial pigments are classified (clustered) based on their physicochemical properties, and representatives of the clusters are screened for QS inhibition. The screen highlighted prodigiosin as a potent quorum quencher, although its production from Serratia marcescens appeared to be QS-independent. In silico analysis indicated potential interactions between AbaI and AbaR, two major QS regulators in A. baumannii, and prodigiosin, which impaired biofilm formation, a major QS-dependent process in the bacteria. Prodigiosin augmented antibiotic action of ciprofloxacin against A. baumannii biofilms. Cell viability analysis revealed prodigiosin to be modestly cytotoxic against HEK293, a non-cancer human cell line. While developing dual-species biofilm, prodigiosin producer S. marcescens significantly impaired the fitness of A. baumannii. Enhanced susceptibility of A. baumannii toward colistin was also noted while growing in co-culture with S. marcescens. Antibiotic resistant isolates demonstrated varied responsiveness against prodigiosin, with two resistant strains demonstrating possible collateral sensitivity. Collectively, the results underpin the prospect of a prodigiosin-based therapeutic strategy in combating A. baumannii infection.

Exploring molecular fingerprints of different drugs having bile interaction: a stepping stone towards better drug delivery.

Bile acids are amphiphilic substances produced naturally in humans. In the context of drug delivery and dosage form design, it is critical to understand whether a drug interacts with bile inside the gastrointestinal (GI) tract or not. This study focuses on the identification of structural fingerprints/features important for bile interaction. Molecular modelling methods such as Bayesian classification and recursive partitioning (RP) studies are executed to find important fingerprints/features for the bile interaction. For the Bayesian classification study, the ROC score of 0.837 and 0.950 are found for the training set and the test set compounds, respectively. The fluorine-containing aliphatic/aromatic group, the branched chain of the alkyl group containing hydroxyl moiety and the phenothiazine ring etc. are identified as good fingerprints having a positive contribution towards bile interactions, whereas, the bad fingerprints such as free carboxylate group, purine, and pyrimidine ring etc. have a negative contribution towards bile interactions. The best tree (tree ID: 1) from the RP study classifies the bile interacting or non-interacting compounds with a ROC score of 0.941 for the training and 0.875 for the test set. Additionally, SARpy and QSAR-Co analyses are also been performed to classify compounds as bile interacting/non-interacting. Moreover, forty-six recently FDA-approved drugs have been screened by the developed SARpy and QSAR-Co models to assess their bile interaction properties. Overall, this attempt may facilitate the researchers to identify bile interacting/non-interacting molecules in a faster way and help in the design of formulations and target-specific drug development.

PDE4 inhibitor eliminates breast cancer stem cells via noncanonical activation of mTOR.

Ineffective cancer treatment is implicated in metastasis, recurrence, resistance to chemotherapy and radiotherapy, and evasion of immune surveillance. All these failures occur due to the persistence of cancer stem cells (CSCs) even after rigorous therapy, thereby rendering them as essential targets for cancer management. Contrary to the quiescent nature of CSCs, a gene profiler array disclosed that phosphatidylinositol-3-kinase (PI3K), which is known to be crucial for cell proliferation, differentiation, and survival, was significantly upregulated in CSCs. Since PI3K is modulated by cyclic adenosine 3',5' monophosphate (cAMP), analyses of cAMP regulation revealed that breast CSCs expressed increased levels of phosphodiesterase 4 (PDE4) in contrast to normal stem cells. In accordance, the effects of rolipram, a PDE4 inhibitor, were evaluated on PI3K regulators and signaling. The efficacy of rolipram was compared with paclitaxel, an anticancer drug that is ineffective in obliterating breast CSCs. Analyses of downstream signaling components revealed a switch between cell survival and death, in response to rolipram, specifically of the CSCs. Rolipram-mediated downregulation of PDE4A levels in breast CSCs led to an increase in cAMP levels and protein kinase A (PKA) expression. Subsequently, PKA-mediated upregulation of phosphatase and tensin homolog antagonized the PI3K/AKT/mTOR pathway and led to cell cycle arrest. Interestingly, direct yet noncanonical activation of mTOR by PKA, circumventing the influence of PI3K and AKT, temporally shifted the fate of CSCs toward apoptosis. Rolipram in combination with paclitaxel indicated synergistic consequences, which effectively obliterated CSCs within a tumor, thereby suggesting combinatorial therapy as a sustainable and effective strategy to abrogate breast CSCs for better patient prognosis.

Evolutionary analysis of globin domains from kinetoplastids.

Globin (Gb) domains function in sensing gaseous ligands like oxygen and nitric oxide. In recent years, Gb domain containing heme binding adenylate cyclases (OsAC or GbAC) emerged as significant modulator of Leishmania response to hypoxia and oxidative stress. During progression of life cycle stages, kinetoplastids experience altered condition in insect vectors or other hosts. Moreover, marked diversity in life style has been accounted among kinetoplastids. Distribution and abundance of Gb-domains vary between different groups of kinetoplastids. While in bodonoids, Gbs are not combined with any other functional domains, in trypanosomatids it is either fused with adenylate cyclase (AC) or oxidoreductase (OxR) domains. In salivarian trypanosomatids and Leishmania (Viannia) subtypes, no gene product featuring Gbs can be identified. In this context, evolution of Gb-domains in kinetoplastids was explored. GbOxR derived Gbs clustered with bacterial flavohemoglobins (fHb) including one fHb from Advenella, an endosymbiont of monoxeneous trypanosomatids. Codon adaptation and other evolutionary analysis suggested that OsAC (LmjF.28.0090), the solitary Gb-domain featuring gene product in Leishmania, was acquired via possible horizontal gene transfer. Substantial functional divergence was estimated between orthologues of genes encoding GbAC or GbOxR; an observation also reflected in structural alignment and heme-binding residue predictions. Orthologue-paralogue and synteny analysis indicated genomic reduction in GbOxR and GbAC loci for dixeneous trypanosomatids.

Exploiting antimicrobial resistance: Better knowledge of resistance mechanisms can inform the search for and development of new antibiotics.

Antibiotic resistance is a grave threat for public health. Understanding the mechanisms of resistance could lead to new drugs and therapeutic strategies against resistant pathogens.

Early detection of lean blowout using recurrence network for varying degrees of premixedness.

Lean premixed combustors are highly susceptible to lean blowout flame instability, which can cause a fatal accident in aircrafts or expensive shutdown in stationary combustors. However, the lean blowout limit of a combustor may vary significantly depending on a number of variables that cannot be controlled in practical situations. Although a large literature exists on the lean blowout phenomena, a robust strategy for early lean blowout detection is still not available. To address this gap, we study a relatively unexplored route to lean blowout using a nonlinear dynamical tool, the recurrence network. Three recurrence network parameters: global efficiency, average degree centrality, and global clustering coefficient are chosen as metrics for an early prediction of the lean blowout. We observe that the characteristics of the time series near the lean blowout limit are highly dependent on the degree of premixedness in the combustor. Still, for different degrees of premixedness, each of the three recurrence network metrics increases during transition to lean blowout, indicating a shift toward periodicity. Thus, qualitatively, the recurrence network metrics show similar trends for different degrees of premixing showing their robustness. However, the sensitivities and absolute trends of the recurrence network metrics are found to be significantly different for highly premixed and partially premixed configurations. Thus, the results indicate that prior knowledge about (i) the degree of premixedness and (ii) the route to lean blowout may be required for accurate early prediction of the lean blowout. We show that the visible structural changes in the recurrence network can be linked to the changes in the recurrence network metrics, helping to better understand the dynamical transition to lean blowout. We observe the power law degree distribution of the recurrence network to break down close to the lean blowout limit due to the intermittent dynamics in the near-LBO regime.

Recurrence network analysis exploring the routes to thermoacoustic instability in a Rijke tube with inverse diffusion flame.

Inverse diffusion flame (IDF) is a reliable low NOx technology that is suitable for various industrial applications including gas turbines. However, a confined IDF may exhibit thermoacoustic instability, a kind of dynamic instability, which is characterized by catastrophically large amplitude pressure oscillations. Transition to such instability for an inverse diffusion flame is less explored compared to other types of flame. In the present study, thermoacoustic instability in a Rijke tube with IDF is achieved by varying air flow rate and input power independently, and the onset of thermoacoustic instability is examined using the framework of recurrence network (RN). During the transition to thermoacoustic instability, we find new routes and two new intermediate states, here referred to as "amplitude varying aperiodic oscillations" and "low amplitude limit cycle-like oscillations." Furthermore, we show that recurrence network analysis can be used to identify the dynamical states during the transition to thermoacoustic instability. We observe an absence of a single characteristic scale, resulting in a non-regular network even during thermoacoustic instability. Furthermore, the degree distributions of RN during combustion noise do not obey a single power law. Thus, scale-free nature is not exhibited during combustion noise. In short, recurrence network analysis shows significant differences in the topological information during combustion noise and thermoacoustic instability for IDF with those for premixed flames, reported earlier.

A comprehensive and comparative study on the action of pentacyclic triterpenoids on Vibrio cholerae biofilms.

While serving as environmental reservoir for V. cholerae infection, biofilms are also crucial for intestinal colonization of the pathogen. Triterpenoids, a group of bioactive phytochemicals, have been tested for antibiofilm activity against model biofilm forming bacteria in recent times. In this context, glycyrrhetinic acid (GRA), ursolic acid (UA) and betulinic acid (BA), representing three categorically distinct groups of pentacyclic triterpenoids, are targeted for profiling their impact on Vibrio cholerae C6709 biofilms. The triterpenoids substantially affected biofilm associated attributes like formation, substratum adherence and dispersion from preformed biofilms. Though at variable degree, the compounds decreased cell surface hydrophobicity and composition in terms of macromolecular content. Not only EPS-associated extracellular enzyme activities were estimated to be reduced by triterpenoid exposure, ultra structural analysis also revealed that GRA, UA and BA can affect extracellular polymeric substance (EPS) content. Albeit total extracellular proteolytic activity remained unaffected by the triterpenoids, GRA treatment resulted in considerable reduction of extracellular gelatinase activity. Molecular docking analysis indicated potential interaction with cyclic di-GMP sensor VpsT, autoinducer-2 sensor kinase LuxP-LuxQ and transcriptional activator HapR, components of complex quorum sensing networks modulating biofilm formation. Comprehensive analysis of antibiotic action revealed accentuation of cephalosporin antibiotics with GRA and UA while BA potentiated action of fluoroquinolones against biofilmed bacteria, widening the scope of combinatorial therapeutic strategy.

Quorum quenching activity of pentacyclic triterpenoids leads to inhibition of biofilm formation by Acinetobacter baumannii.

The quorum quenching (QQ) potential of three pentacyclic triterpenoids, glycyrrhetinic acid (GRA), ursolic acid (UA) and betulinic acid (BA), representing distinct groups of compounds, was evaluated. Violacein production by Chromobacterium violaceum and pyocyanin production by Pseudomonas aeruginosa were severely affected by GRA, UA and BA, suggesting a perturbation of N-acyl homoserine lactone (ASL) based signaling. Molecular docking analysis revealed a possible interaction between ASL-synthase and ASL-dependent transcriptional activator homologs from P. aeruginosa and Acinetobacter baumannii with common binding pockets for GRA, UA and BA. The triterpenoids inhibited biofilm formation by A. baumannii and affected the overall structure of biofilms. When administered in combination, two of the three molecules fostered antibiotic action against A. baumannii biofilms, widening the scope for developing novel combinations against the pathogen.

Application of recurrence quantification analysis for early detection of lean blowout in a swirl-stabilized dump combustor.

Lean blowout (LBO) is a serious issue in modern gas turbine engines that operate in a lean (premixed) mode to follow the stringent emission norms. When an engine operates with a lean fuel-air mixture, the flame becomes unstable and is at times carried out of the combustion chamber by the unburnt flow. Thus, the sudden loss of the flame, known as lean blowout, leads to fatal accidents in aircrafts and loss of production in power plants. Therefore, an in-depth analysis of lean blowout is necessary as the phenomenon involves complex interactions between flow dynamics and chemical kinetics. For understanding the complex dynamics of this phenomenon, recurrence analysis can be a very useful method. In the current study, we observe a transition to LBO as the global fuel-air ratio is reduced from stoichiometric condition and perform recurrence quantification analysis (RQA) with the CH∗ chemiluminescence data obtained experimentally. The extent of fuel-air mixing is varied with an objective of developing some robust early predictors of LBO that would work over a wide range of premixing. We find some RQA measures, such as determinism, laminarity, and trapping time, which show distinctive signature toward LBO and thereby can be used as early predictors of LBO for both premixed and partially premixed flames. Our analysis shows that the computational time for laminarity and trapping time is relatively less. However, computational time for those measures depends upon the dynamics of the combustor, size of the data taken, and choice of recurrence threshold.

Gain- and Loss-of-Function Screens Coupled to Next-Generation Sequencing for Antibiotic Mode of Action and Resistance Studies in Streptococcus pneumoniae.

Two whole-genome screening approaches are described for studying the mode of action and the mechanisms of resistance to trimethoprim (TMP) in the Gram-positive Streptococcus pneumoniae The gain-of-function approach (Int-Seq) relies on a genomic library of DNA fragments integrated into a fucose-inducible cassette. The second approach, leading to both gain- and loss-of-function mutation, is based on chemical mutagenesis coupled to next-generation sequencing (Mut-Seq). Both approaches pointed at the drug target dihydrofolate reductase (DHFR) as a major resistance mechanism to TMP. Resistance was achieved by dhfr overexpression either through the addition of fucose (Int-Seq) or by mutations upstream of the gene (Mut-Seq). Three types of mutations increased expression by disrupting a predicted Rho-independent terminator upstream of dhfr Known and novel DHFR mutations were also detected by Mut-Seq, and these were functionally validated for TMP resistance. The two approaches also suggested that an increase in the metabolic flux from purine synthesis to GTP and then to folate can modulate the susceptibility to TMP. Finally, we provide evidence for a novel role of the ABC transporter PatAB in TMP susceptibility. Our genomic screens highlighted novel aspects on the mode of action and mechanisms of resistance to antibiotics.

Exploration of Fingerprints and Data Mining-based Prediction of Some Bioactive Compounds from Allium sativum as Histone Deacetylase 9 (HDAC9) Inhibitors.

BACKGROUND: Histone deacetylase 9 (HDAC9) is an important member of the class IIa family of histone deacetylases. It is well established that over-expression of HDAC9 causes various types of cancers including gastric cancer, breast cancer, ovarian cancer, liver cancer, lung cancer, lymphoblastic leukaemia, etc. The important role of HDAC9 is also recognized in the development of bone, cardiac muscles, and innate immunity. Thus, it will be beneficial to find out the important structural attributes of HDAC9 inhibitors for developing selective HDAC9 inhibitors with higher potency. METHODS: The classification QSAR-based methods namely Bayesian classification and recursive partitioning method were applied to a dataset consisting of HADC9 inhibitors. The structural features strongly suggested that sulphur-containing compounds can be a good choice for HDAC9 inhibition. For this reason, these models were applied further to screen some natural compounds from Allium sativum. The screened compounds were further accessed for the ADME properties and docked in the homology-modelled structure of HDAC9 in order to find important amino acids for the interaction. The best-docked compound was considered for molecular dynamics (MD) simulation study. RESULTS: The classification models have identified good and bad fingerprints for HDAC9 inhibition. The screened compounds like ajoene, 1,2 vinyl dithiine, diallyl disulphide and diallyl trisulphide had been identified as compounds having potent HDAC9 inhibitory activity. The results from ADME and molecular docking study of these compounds show the binding interaction inside the active site of the HDAC9. The best-docked compound ajoene shows satisfactory results in terms of different validation parameters of MD simulation study. CONCLUSION: This in-silico modelling study has identified the natural potential lead (s) from Allium sativum. Specifically, the ajoene with the best in-silico features can be considered for further in-vitro and in-vivo investigation to establish as potential HDAC9 inhibitors.

Repurposing approved protein kinase inhibitors as potent anti-leishmanials targeting Leishmania MAP kinases.

AIMS: Leishmaniasis, caused by the protozoan parasite poses a significant health burden globally. With a very few specific drugs, increased drug resistance it is important to look for drug repurposing along with the identification of pre-clinical candidates against visceral leishmaniasis. This study aims to identify potential drug candidates against visceral leishmaniasis by targeting leishmanial MAP kinases and screening FDA approved protein kinase inhibitors. MATERIALS AND METHODS: MAP kinases were identified from the Leishmania genome. 12 FDA approved protein kinase inhibitors were screened against Leishmania MAP kinases. Binding affinity, ADME and toxicity of identified drug candidates were profiled. The anti-proliferative effects and mechanism of action were assessed in Leishmania, including changes in cell morphology, flagellar length, cell cycle progression, reactive oxygen species (ROS) generation, and intra-macrophage parasitic burden. KEY FINDINGS: 23 MAP kinases were identified from the Leishmania genome. Sorafenib and imatinib emerged as repurposable drug candidates and demonstrated excellent anti-proliferative effects in Leishmania. Treatment with these inhibitors resulted in significant changes in cell morphology, flagellar length, and cell cycle arrest. Furthermore, sorafenib and imatinib promoted ROS generation and reduced intra-macrophage parasitic burden, and elicited anti-leishmanial activity in in vivo experimental VL models. SIGNIFICANCE: Collectively, these results imply involvement of MAP kinases in infectivity and survival of the parasite and can pave the avenue for repurposing sorafenib and imatinib as anti-leishmanial agents. These findings contribute to the exploration of new treatment options for visceral leishmaniasis, particularly in the context of emerging drug resistance.

A chitosan-α-naphthaldehyde hydrogel film containing pineapple leaf fibers for wound dressing applications.

In recent decades, polysaccharide-based hydrogels have gained significant attention due to their natural biocompatibility, biodegradability, and non-toxicity. The potential for using polysaccharides to synthesize hydrogels is due to their ability to support cell proliferation, which is important for practical applications, particularly in the biomedical field. In this study, we have synthesized a chitosan-α-naphthal hydrogel film using a cost-effective one-step synthesis approach. The prepared hydrogel film exhibited high encapsulation efficiency for antibacterial drugs such as ciprofloxacin and lomefloxacin, with the ability to release the antibiotics in a controlled manner over an extended period and prevent long-term bacterial infections. Moreover, the Korsmeyer and Peppas power law, based on Fickian diffusion, was employed to model the entire complex drug release process and predict the drug release behavior. The hydrogel film also shows pH-induced swelling ability due to the presence of an imine bond in the hydrogel network, which is degradable at acidic pH. The incorporated therapeutic agents having antibacterial activity were effective against Gram-negative (Escherichia coli DH5α) and Gram-positive (Staphylococcus aureus subsp. aureus) bacterial strains. A wound dressing material should possess mechanical strength, but the prepared hydrogel film has low mechanical strength. To increase the mechanical strength, we have infused pineapple leaf fibers (PLFs) in the film network, resulting in a mechanical strength of 1.12 ± 0.89 MPa. In addition to its mechanical strength, significant cell viability against human embryonic kidney (HEK-293) cells was observed from in vitro cell culture experiments for this PLF-hydrogel film. As a result, the prepared therapeutic agent-loaded hydrogel film under study meets the requirements to be considered for use as a wound dressing material.

New Cyanostyrylcopillar[5]arene Derivative: Synthesis, Photophysical Study, Chromogenic Detection of Aliphatic Amines, and Biofilm-Antibiofilm Activity.

The synthesis, characterization, and application of a new cyanostyrylcopillar[5]arene 1 is reported. Single-crystal X-ray diffraction and other spectroscopic techniques confirm the identity of the new copillar 1. The X-ray diffraction study reveals that the copillar 1 exhibits a 1D supramolecular chain in the solid state involving π···π interactions along the crystallographic c-axis and 1D chains are further connected by interchain C-H···π interactions to establish 2D supramolecular layers within the crystallographic bc-plane. 2D supramolecular chains on further packing introduce a 3D structure with void spaces filled with hexane molecules. Through minimal deviation in the dihedral angle, the cyano-substituted ethylenic group in 1 shows a conjugation with the phenolic -OH, favoring intramolecular bond conjugation (ITBC) and colorimetrically detects the aliphatic amines over aromatic amines in CH3CN. Among the aliphatic amines, tertiary amines are differentiated from primary and secondary amines by the naked eye through color change. Both in solution and solid states, 1 displays vapor phase detection of volatile aliphatic amines. Antibacterial activity analysis shows that while 1 exhibits the antibiofilm action against Gram-positive pathogenic bacteria, Staphylococcus aureus, it promotes biofilm formation by Gram-negative pathogenic bacteria, Pseudomonas aeruginosa.

Identification of a protein kinase A regulatory subunit from Leishmania having importance in metacyclogenesis through induction of autophagy.

cAMP-mediated responses act as modulators of environmental sensing and cellular differentiation of many kinetoplastidae parasites including Leishmania. Although cAMP synthesizing (adenylate cyclase) and degrading (phosphodiesterase) enzymes have been cloned and characterized from Leishmania, no cAMP-binding effector molecule has yet been identified from this parasite. In this study, a regulatory subunit of cAMP-dependent protein kinase (Ldpkar1), homologous to mammalian class I cAMP-dependent protein kinase regulatory subunit, has been identified from L. donovani. Further characterization suggested possible interaction of LdPKAR1 with PKA catalytic subunits and inhibition of PKA activity. This PKA regulatory subunit is expressed in all life cycle stages and its expression attained maximum level in stationary phase promastigotes, which are biochemically similar to the infective metacyclic promastigotes. Starvation condition, the trigger for metacyclogenesis in the parasite, elevates LdPKAR1 expression and under starvation condition promastigotes overexpressing Ldpkar1 attained metacyclic features earlier than normal cells. Furthermore, Ldpkar1 overexpression accelerates autophagy, a starvation-induced cytological event necessary for metacyclogenesis and amastigote formation. Conditional silencing of Ldpkar1 delays the induction of autophagy in the parasite. The study, for the first time, reports the identification of a functional cAMP-binding effector molecule from Leishmania that may modulate important cytological events affecting metacyclogenesis.