LSM - Seminars: April 2009 Archives

Seminars Archives

March 2009 | April 2009 | May 2009

Thursday, April 02, 2009
Nanotechnology approaches for identifying multiple cues regulating stem/cancer cell fate KiBum Lee Department of Chemistry & Chemical Biology Rutgers University Thursday, April 2, 2009 12:00 Noon, Chem 260 This talk will focus on the interface of micro-/nano science and cell biology. Even though cell fate (e.g. stem cell differentiation and cancer cell apoptosis) is regulated by interactions with microenvironment cues and intrinsic cellular programs, understanding the functions of microenvironments and manipulating gene expression in stem/cancer cells are hampered by limitations of conventional methods and the lack of extensive knowledge of multiple regulatory signals. If the complex cell behaviors are to be fully investigated, both approaches from nanotechnology—the “top-down” patterning of extracellular matrix (ECM) and signal molecules in combinatorial ways (e.g. ECM compositions, pattern geometry, pattern density and gradient patterns), and the “bottom-up” synthesis of multifunctional nanoparticles and their surface modification with specific signal molecules—should be combined synergistically. To address the aforementioned challenge, our research mainly focuses on three approaches: i) development of combinatorial arrays of microenvironmental signal molecules for investigating cell behaviors; ii) synthesis and utilization of multifunctional nanoparticles as chemotherapeutic reagents against glioblastoma multiforme (GBM); and iii) development of a microfluidic assay platform to identify the optimal conditions for stem cell differentiation and self-renewal. More specifically, we have applied the combinatorial signal arrays to study the temporal/spatial effect of microenvironmental cues on adhesion, growth, differentiation of functional cells (e.g. neural stem cells and glioblastoma cells). Furthermore, novel synthetic approaches for anti-cancer drugs [e.g. Erlotinib and Histone deacetylase inhibitors (HDAC inhibitors)] and modified siRNA to be linked with nanoparticles have been developed. In parallel research efforts, we have developed a high throughput screening method based on microfluidics to study human embryonic stem cell (hESCs) responses toward multiple microenvironmental cues at the single cell level. In this talk, a summary of the results from these efforts and future directions will be discussed.

Thursday, April 02, 2009

Nanotechnology approaches for identifying multiple cues regulating stem/cancer cell fate
KiBum Lee
Department of Chemistry & Chemical Biology
Rutgers University
Thursday, April 2, 2009
12:00 Noon, Chem 260

This talk will focus on the interface of micro-/nano science and cell biology. Even though cell fate (e.g. stem cell differentiation and cancer cell apoptosis) is regulated by interactions with microenvironment cues and intrinsic cellular programs, understanding the functions of microenvironments and manipulating gene expression in stem/cancer cells are hampered by limitations of conventional methods and the lack of extensive knowledge of multiple regulatory signals. If the complex cell behaviors are to be fully investigated, both approaches from nanotechnology—the “top-down” patterning of extracellular matrix (ECM) and signal molecules in combinatorial ways (e.g. ECM compositions, pattern geometry, pattern density and gradient patterns), and the “bottom-up” synthesis of multifunctional nanoparticles and their surface modification with specific signal molecules—should be combined synergistically. To address the aforementioned challenge, our research mainly focuses on three approaches: i) development of combinatorial arrays of microenvironmental signal molecules for investigating cell behaviors; ii) synthesis and utilization of multifunctional nanoparticles as chemotherapeutic reagents against glioblastoma multiforme (GBM); and iii) development of a microfluidic assay platform to identify the optimal conditions for stem cell differentiation and self-renewal. More specifically, we have applied the combinatorial signal arrays to study the temporal/spatial effect of microenvironmental cues on adhesion, growth, differentiation of functional cells (e.g. neural stem cells and glioblastoma cells). Furthermore, novel synthetic approaches for anti-cancer drugs [e.g. Erlotinib and Histone deacetylase inhibitors (HDAC inhibitors)] and modified siRNA to be linked with nanoparticles have been developed. In parallel research efforts, we have developed a high throughput screening method based on microfluidics to study human embryonic stem cell (hESCs) responses toward multiple microenvironmental cues at the single cell level. In this talk, a summary of the results from these efforts and future directions will be discussed.

Thursday, April 09, 2009
IAMDN Focus Session

Thursday, April 16, 2009
Nonlinear optical studies of structure and dynamics at aqueous interfaces Eric Borguet, Temple University 12:00 Noon, Chem. 260 The structure of water at interfaces is known to be different from the bulk, and depends on many parameters including chemical composition of the interface, the surface charge, and the ionic strength of the solution. While there have been many spectroscopic investigations of interfacial water, its ultrafast vibrational dynamics is significantly less well understood. Using IR pump-vibrational Sum Frequency Generation our group has probed the vibrational dephasing and vibrational relaxation of the O-H stretch in the hydrogen bonded region at aqueous interfaces. Contrary to previous reports, the ordering of interfacial water at the silica interface leads to a dramatic acceleration of vibrational relaxation. The vibrational lifetime of the O-H stretch of water at the charged silica/water interface is ~ 200 fs, a factor 2-3 shorter than when the surface is neutral. We will also report the effect of ionic strength on the vibrational dynamics. The observed acceleration of the interfacial vibrational dynamics reflects the increased hydrogen bonding of water at the charged interface and is consistent with the theoretical framework of the dependence of bulk dynamics on structure.

Thursday, April 16, 2009

Nonlinear optical studies of structure and dynamics at aqueous interfaces
Eric Borguet,
Temple University
12:00 Noon, Chem. 260

The structure of water at interfaces is known to be different from the bulk, and depends on many parameters including chemical composition of the interface, the surface charge, and the ionic strength of the solution. While there have been many spectroscopic investigations of interfacial water, its ultrafast vibrational dynamics is significantly less well understood. Using IR pump-vibrational Sum Frequency Generation our group has probed the vibrational dephasing and vibrational relaxation of the O-H stretch in the hydrogen bonded region at aqueous interfaces. Contrary to previous reports, the ordering of interfacial water at the silica interface leads to a dramatic acceleration of vibrational relaxation. The vibrational lifetime of the O-H stretch of water at the charged silica/water interface is ~ 200 fs, a factor 2-3 shorter than when the surface is neutral. We will also report the effect of ionic strength on the vibrational dynamics. The observed acceleration of the interfacial vibrational dynamics reflects the increased hydrogen bonding of water at the charged interface and is consistent with the theoretical framework of the dependence of bulk dynamics on structure.

Thursday, April 23, 2009
Energy Harvesting and Storage with Thermogalvanic Cells Nick Hudak & Glenn G. Amatucci, ESRG, Rutgers 12:00 Noon, Chem. 260 For many applications, the nodes in a wireless sensor network must be cubic-millimeter sized and have a long lifetime. The amount of energy that can be stored in a sensor node is determined by its size. A cubic-millimeter-sized node with a battery as the sole power source has a severely limited lifetime. Alternatively, energy harvesting devices may be used to recharge the battery or to directly power the sensor and communication components, thus allowing for small nodes with unlimited lifetime. Small-scale energy harvesting devices based on thermoelectric, vibration, and radiofrequency power conversion have been considered for this purpose. An alternative type of thermal energy harvesting, based on thermogalvanic cells, accomplishes both energy harvesting and energy storage in the same device. This multi-functionality is an important space-saving advantage because it eliminates the need for an interface between the energy harvester and the battery. A thermogalvanic cell (or non-isothermal cell) is an electrochemical cell in which the two electrodes are at different temperatures. In symmetric thermogalvanic cells (those with compositionally identical electrodes), the temperature gradient produces a proportional voltage output. The voltage per degree temperature difference in thermogalvanic cells is typically ~1 mV/K or higher, which is four to five times higher than that of the best thermoelectric materials. Unlike the thermoelectric Seebeck effect, thermogalvanic voltage is closely related to the partial molar entropy of the electrode reaction and the thermal diffusion potential of the electrolyte. A thermogalvanic cell with symmetric, single-phase intercalation electrodes undergoes a charge-discharge cycle when supplied with oscillating heat flow. Partial-molar entropies and thermogalvanic measurements for a range of electrode-electrolyte combinations will be presented in order to identify materials that provide the best performance in such cells.

Thursday, April 23, 2009

Energy Harvesting and Storage with Thermogalvanic Cells
Nick Hudak & Glenn G. Amatucci, ESRG, Rutgers
12:00 Noon, Chem. 260

For many applications, the nodes in a wireless sensor network must be cubic-millimeter sized and have a long lifetime. The amount of energy that can be stored in a sensor node is determined by its size. A cubic-millimeter-sized node with a battery as the sole power source has a severely limited lifetime. Alternatively, energy harvesting devices may be used to recharge the battery or to directly power the sensor and communication components, thus allowing for small nodes with unlimited lifetime. Small-scale energy harvesting devices based on thermoelectric, vibration, and radiofrequency power conversion have been considered for this purpose. An alternative type of thermal energy harvesting, based on thermogalvanic cells, accomplishes both energy harvesting and energy storage in the same device. This multi-functionality is an important space-saving advantage because it eliminates the need for an interface between the energy harvester and the battery. A thermogalvanic cell (or non-isothermal cell) is an electrochemical cell in which the two electrodes are at different temperatures. In symmetric thermogalvanic cells (those with compositionally identical electrodes), the temperature gradient produces a proportional voltage output. The voltage per degree temperature difference in thermogalvanic cells is typically ~1 mV/K or higher, which is four to five times higher than that of the best thermoelectric materials. Unlike the thermoelectric Seebeck effect, thermogalvanic voltage is closely related to the partial molar entropy of the electrode reaction and the thermal diffusion potential of the electrolyte. A thermogalvanic cell with symmetric, single-phase intercalation electrodes undergoes a charge-discharge cycle when supplied with oscillating heat flow. Partial-molar entropies and thermogalvanic measurements for a range of electrode-electrolyte combinations will be presented in order to identify materials that provide the best performance in such cells.

Thursday, April 30, 2009
Conductance of Single Molecules Circuits Dr. Latha Venkataraman, Columbia University 12:00 Noon,Chem. 260 Understanding the transport characteristics of molecules bonded between metal electrodes is of fundamental importance for molecular scale electronics. It is well known that these transport characteristics are influenced by the intrinsic properties of the molecules, including their length, conformation, the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and the alignment of this gap to the metal Fermi level. This talk will focus on the relation between intrinsic molecular properties, including molecular link chemistry and the conductance of single molecule junctions formed by breaking gold point-contacts in an environment of molecules. The relation between molecular conductance and molecule conformation for the simple case of a biphenyl, two benzene rings linked together by a single C-C bond will be presented. Specifically, I will show that for a series of biphenyl derivatives, the molecular junction conductance decreases with increasing twist angle, following a cosine squared dependence. I will also show that for substituted benzenes, the conductance varies inversely with the calculated ionization potential of the molecules, indicating that the tunneling transport in these molecules is analogous to hole tunneling through an insulating film. Finally, I will discuss some new results with pyridine linked molecules, and demonstrate mechanically activated switching in these single molecule junctions.

Thursday, April 30, 2009

Conductance of Single Molecules Circuits
Dr. Latha Venkataraman,
Columbia University
12:00 Noon,Chem. 260

Understanding the transport characteristics of molecules bonded between metal electrodes is of fundamental importance for molecular scale electronics. It is well known that these transport characteristics are influenced by the intrinsic properties of the molecules, including their length, conformation, the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and the alignment of this gap to the metal Fermi level. This talk will focus on the relation between intrinsic molecular properties, including molecular link chemistry and the conductance of single molecule junctions formed by breaking gold point-contacts in an environment of molecules. The relation between molecular conductance and molecule conformation for the simple case of a biphenyl, two benzene rings linked together by a single C-C bond will be presented. Specifically, I will show that for a series of biphenyl derivatives, the molecular junction conductance decreases with increasing twist angle, following a cosine squared dependence. I will also show that for substituted benzenes, the conductance varies inversely with the calculated ionization potential of the molecules, indicating that the tunneling transport in these molecules is analogous to hole tunneling through an insulating film. Finally, I will discuss some new results with pyridine linked molecules, and demonstrate mechanically activated switching in these single molecule junctions.

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