S. Ray

Insensitivity to the α2-adrenergic receptor blocker yohimbine hydrochloride and occurrence of spontaneous platelet macroaggregation (SPMA) in diabetes

We report here a study of platelet aggregation in diabetes, induced by epinephrine and its inhibition by yohimbine hydrochloride (YH), an α2-adrenergic receptor-blocking agent. Interestingly, emergence of spontaneous platelet macroaggregation (SPMA) was observed in six out of 75 cases in the absence of any agonist. The SPMA cases were strongly associated with insensitivity to YH (in contrast with non-SPMA cases) when epinephrine was used as an agonist. We suggest that the observed correlation is a result of over expression of platelet α2-adrenoceptors in such subjects. The quantitative nature of the effect is supported by the observation that addition of YH at higher concentration (more than 5 µM) led to restoration of the adrenergic receptor-blocking activity of the said agent. Eventually for non-SPMA subjects YH exhibited blocking activity even at lower concentration. The aggregation profile and the platelet morphology of the SPMA cases had distinctive features as compared to microaggregates formed in other diabetic subjects (non-SPMA cases).

Cross talk between photo-pigments and graphene electron cloud - Designing a biodiode

We report emergence of a new electrical material by growing photosynthetic biofilm on a Dirac material, graphene. The material showed new conducting as well as semiconducting properties. Frequency dependent capacitive spectra further indicated presence of electrical isosbestic points(at 0.8 and 9MHz), implying two state dieletric transitions at critical frequencies. A notable reult was a Schottky diode like behavior in the IV curve. Voltage dependent conductance with conductance peaks near the Schottky diode threshold was observed. We obtained facilitated growth of photosynthetic biofilm in presence of graphene. Lastly higher bacterial metabolism was seen in graphene incorporated biofilm. For this zero band gap Dirac material this can only be interpreted as coupling of the electron transport chain of the bacterial biofilm and the graphene electron cloud.

Light Amplification By Biofilm And Its Polarization Dependence

We report amplified, transmitted light intensity, compared to input, when photosynthetic biofilms were placed in the path of Rayleigh scattered, monochromatic light. Enhancement spectrum shows peak at around 505 nm, which corresponds to the pore wall thickness in biofilm ultra-structure, suggesting role of resonant Mie scattering. Enhancement factors differed when biofilms from different stages of growth were used. Enhancement factors were found to depend on the nature of Rayleigh scattering liquid. Polarizing Rayleigh scattered light by the use of polarizers affected the percentage of enhancement. Amplified output is achievable with constructive interference arising out of coherent forward light scattering, a theoretically predicted outcome of Anderson localization of photons. Possible uses of photosynthetic biofilms in organic material based photonic devices have been discussed.

Switchable amplification of fluoresence from a photosynthetic microbe

One known attribute of the photosynthetic apparatus is photon capture and generation of metabolic energy. The thermodynamic implications of fluorescence, invariably associated with the photosynthetic components is however poorly understood. In this paper we report a density dependent amplification of such fluorescence which can be interpreted as a thermodynamic strategy of controlled energy release by the cell. We show in support of this hypothesis that prolonged photo-exitation of cell free extract of Rhodobacter capsulatus SB1003 at 395 nm, induces fluorescence emission amplifying with time as long as the fluorophore density is above a critical level. The fact that the amplification disappears at low temperature and at dilute condition, is in accordance with the thermodynamic interpretation that energy is released as per requirement. Live cell imaging is also validation of the phenomenon even at the cellular level. Single cells of Rhodobacter capsulatus SB1003 shows time dependent loss of fluorescence, the process being reversed for cellular clusters. To explain the mechanism of this bistable fluorescence (F) amplification, variation of the scale free kinetic constant k=1/F (dF/dt) is studied at varying temperatures in presence and absence of static magnetic field. The sign of k shifts from positive to negative if T is lowered or if the system is diluted. But at low T, k again switches from negative to positive value, if static magnetic field is applied. The chain of events can be explained by a simple model assuming excretion of a porphyrin by the microbe and possible photon dependent aggregation behavior of such porphyrin complex, differential temperature and magnetic field sensitivity of the monomeric or aggregated forms of porphyrin being reported earlier.

Bistability In Fluorescence From A Purple Non-Sulfur Bacteria

Bistable optical emission has been observed for photosynthetic purple non-sulfur bacteria Rhodobacter capsulatus SB1003. The microbes respond to UV excitation (at 395nm) in a bifurcating way one branch corresponding to increase and the other corresponding to diminishing fluorescent emission in the range 590-685nm.The switching between such bifurcating branches can be observed when parameters like concentration, temperature are varied or static magnetic field is applied. Thus switching from amplification to reduction occurs if fluorophore concentration lowered. Again if temperature is lowered a steady quenching (instead of amplification) of fluorescence is observed. However presence of magnetic field of the order of 0.5 T reverts this and once again the systems resumes its fluoresence amplifying state. We propose that aggregation of bacterial porphyrin and regulation of such aggregation by photon excitation may explain this bistablity. Possible ecological implication of the photosynthetic bistability is suggested.

Emerging Electrical Properties of Graphene incorporated Photosynthetic Biofilms

Biofilms have been a breeding ground for creation of novel biomaterials with emergent properties. We report immobilization of hydrophobic graphene by a growing photosynthetic biofilm. We obtained a conductive biomaterial that can form a Schottky diode when grown on a metallic electrode surface. Capacitive spectra on frequency axis were obtained for control biofilm, which showed isosbestic points at 0.9 and 6MHz when RMS voltage was changed. This implies a two state di-electric transition. Immobilization of graphene by biofilm shifts such electrical isosbestic points significantly. The additional implication of the present study is the emergence of voltage dependent conductance with conductance peaks near the Schottky diode threshold. The observed emergent properties may be helpful in biomaterial based design of sensors.We report emergence of a new electrical material by growing photosynthetic biofilm on a Dirac material, graphene. The material showed new conducting as well as semiconducting properties. Frequency dependent capacitive spectra further indicated presence of electrical isosbestic points(at 0.8 and 9MHz), implying two state dieletric transitions at critical frequencies. A notable reult was a Schottky diode like behavior in the IV curve. Voltage dependent conductance with conductance peaks near the Schottky diode threshold was observed. We obtained facilitated growth of photosynthetic biofilm in presence of graphene. Lastly higher bacterial metabolism i was seen in the biofilm in contact with graphene as compared to its normal growth condition. For this zero band gap Dirac material this can only be interpreted as coupling of the electron transport chain of the bacterial biofilm and the graphene electron cloud.

Probiotics as cheater cells: Parameter space clustering for individualized prescription

Clinicians often perform infection management administering probiotics along with antibiotics. Such probiotics added to an infecting population showing antibiotic resistance can be compared to a dynamical system composed of cheaters and workers. The presence of cheater strains is known to modulate the fitness of the infecting population. We propose a model where probiotics as cheater strain re-establishes the susceptibility of a resistant population towards an antibiotic. Control parameters must assume optimal values in order to attain minimum worker number within a finite time-scale feasible in a clinical set-up. The problem is made non-trivial by the complicated interplay between parameters. The model is an extension of a logistic framework, where a pay-off function has been included to account for the effect of instantaneous worker number on death rates of each species. The outcomes for a randomized set of parameter values and initial conditions are utilized in partitioning the set and desired clusters were identified. For a test case, one can take random combinations of controllable parameters and combine them with fixed parameters and find out the closeness of the points to the desired cluster centroids. This process leads to the identification of optimum antibiotic versus probiotic dosage range leading to elimination or limited existence of the genetically resistant population.