Integrated Calendar

At BARC, we have been making efforts to fabricate hybrid electronic components, such as, a dielectric, rectifier, resonant tunnel diode, FET and memory, using self-asssembled mono/multilayers on Si. In this talk we shall touch upon some aspects related to our recent studies, viz. the electrografting of organic molecules on Si; design of new porphyrin-based sigma-pi molecules and the observation of memory effect and diode action in them; observation of NDR effect for LbL-grown APTMS films as well as electrografted DFTT films; and transport effects in O-MBE grown TM-phthalocyanine films.Very recently, we have embarked on the development of photoelectrochemical cells (PEC), too. Preliminary results on two different PEC systems will be described.

All organisms rely on noisy molecular recognition to convey, process and store information. This stochastic biophysical setting poses a tough challenge: how to construct information processing systems that are efficient and economical yet error-resilient? I will review recent results that reveal generic design principles of molecular information systems. This biological design problem turns out to be equivalent to the statistical physics of stochastic maps and optimization processes. The examples considered range from molecular codes [1] through molecular recognition and homologous recombination (a crucial mechanism of sexual reproduction that yields genetic diversity) [2] to the spatial organization of chromosomes in the cell nucleus.

[1] Tlusty, PRL 100, 048101 (2008); PNAS 105, 8238-8243 (2008); Phys Life Rev 7, 362-376 (2010).

[2] Savir et al., PNAS 107, 3475-80 (2010); Mol Cell 40(3), 388-396 (2010).

The talk will start with a basic introduction aimed at the non-expert.

In response to external stimuli, cells adjust their behavior to a changing environment – for example, they start to divide or migrate. In order to perform these actions, the protein content of the cell must change. To accomplish this, a cell must modify the levels at which the genes that code for these proteins are transcribed. These transcriptional responses to extracellular stimuli are regulated by tuning the rates of transcript production and degradation. I present here the results of a study aimed at deducing the dynamics of these two processes from measurements of the transcriptome, and to elucidate the operational strategy behind this dynamics.

By combining a simple theoretical model of transcription with simultaneous measurements of time-dependent precursor mRNA and mature mRNA abundances, we were able to infer unexpected complex stimulation-induced time-dependent transcript production and degradation. In particular, we found that production of many transcripts was characterized by a large dynamic range, which allowed these genes to exhibit an unexpectedly strong transient “production overshoot”, thereby accelerating their induction.