Subject: [Depfis] anuncio de coloquios martes 19 y jueves 21

From: Silvina Ponce Dawson <[email-masked]>
Date: Mon, 18 Feb 2013 13:56:56 -0300

Hola a todos,
les paso aca la informacion de dos charlas que se van a dar en el
Depto de Quimica Biologica (maniana) y en el Laboratorio de Fisiologia
y Biologia Molecular y Celular (el jueves). Se trata de dos
investigadores que estan visitando a Alejandro Colman-Lerner del
LFBMC.
Saludos
silvina

Seminario 1.

Martes 19, 2:30pm aula Cardini del depto Química Biológica.

Prof. Dr. Andreas Herrmann-

Humboldt-Universität zu Berlin
Institut für Biologie
Molekulare Biophysik
Invalidenstr. 42
D-10115 Berlin, Germany
Email: [email-masked]

Influenza virus belongs to a wide range of enveloped viruses.
Virus-host cell binding marks the first critical step of infection.
Hence, forces
involved in this process are essential. The major spike protein
hemagglutinin binds sialic acid residues of glycoproteins and lipids
with dissociation constants in the millimolar range (Sauter et al.
(1992) Biochemistry 31:9609–9621), indicating a multivalent binding
mode. We characterized the attachment of influenza virus to host cell
receptors
using three independent approaches. Optical tweezers and atomic force
microscopy-based single molecule force spectroscopy provides powerful
tools to measure binding forces in biological systems. Optical
tweezers and AFM-based single molecule force spectroscopy revealed
very low
interaction forces.  The observation of sequential unbinding events
strongly suggests a multivalent binding mode between virus and cell
membrane. However, an assignment of forces to their underlying
molecular interactions involved in these processes is difficult or
even cannot be
obtained by these techniques. In molecular dynamics, time-dependent
interactions between all atoms within a given system are calculated
numerically within timescales smaller than those observed in
biological phenomena. Force probe molecular dynamics simulations
provide a way to
overcome this time limitation by introducing a moving harmonic
potential as a "virtual spring" acting on given atoms. Molecular
dynamics
simulations reveal a variety of unbinding pathways that indicate a
highly dynamic interaction between HA and its receptor allowing to
rationalize
the binding of influenza virus to host cells quantitatively at molecular level.

Seminario 2:

Jueves 21 a la 1pm en el aula de seminarios del LFBM:

Mathematical modeling of yeast stress response and cell cycle regulation
Edda Klipp

Humboldt-Universität zu Berlin, Theoretical Biophysics

Cells have to grow and to divide. This is a well-organized, highly
regulated process. Since
cells also have to react to changes in the environment, cell cycle
must be both robust against and sensitive to changes. The ability to
perceive and respond to information from their environment is one of
the most ubiquitous properties of cellular organisms. It is crucial
for a cell to react appropriately to changes or signals in its
environment. This becomes apparent in many situations such as the
search for nutrients, the detection of potentially harmful external
conditions and in cell-cell communication as it is required for any
multi-cellular organism. Even though there is a huge selection of
perceivable signals the underlying mechanisms are surprisingly alike,
which suggests that they are highly conserved in the course of
evolution. Here, we apply different modeling techniques to understand
cell cycle progression and cell cycle regulation in changing
environments, with specific focus on mechanisms and experimental data
for the model organism Saccharomyces cerevisiae. Specifically, new
aspects in cell cycle regulation and the interaction of
stress-activated signaling pathways with cell cycle progression will
be discussed. The results indicate that yeast cells have developed
different mechanisms for coping with external stress during different
periods of their life time.

-- 
Silvina Ponce Dawson
Depto Fisica e IFIBA-CONICET
FCEN-UBA
Ciudad Universitaria, Pab I
(1428) Buenos Aires, Argentina
Phone: (5411) 4576 3353
Fax: (5411) 4576 3357