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May 4, 2021 Webinar Speakers

Our next webinar will take place via the internet on Tuesday May 4th at 11AM EDT/4PM GMT. Sign up on our mailing list to receive the Zoom link!

We hope to see/hear from you all at one of our sessions or as one of the next speakers. If you are an early career scientist and would like to present your research, don't hesitate to submit an abstract today! For now, please learn more about our current speakers and their research below. We also thank the generous support from Cell Reports Physical Science.

Our featured speakers this week are Laia Delgado Callico (PhD student, King's College London, UK), Dr. Sreetama Pal (Centre for Cellular and Molecular Biology, India) and Dr. Timothy Dreier (postdoc, Sandia National Laboratory, USA). The seminar will be guest moderated by Dr. Dani Schultz from Merck.


LAIA DELGADO CALLICO (on twitter @LaiaDelCa)

Biography: Laia is a PhD student in the Physics department, she studies metallic nanoparticles using molecular dynamics and quantum chemical calculations. Her research focuses on their physical and chemical properties such as magnetism, vibrational and optical spectra, electronic structure, and thermodynamics. Before starting her PhD, Laia obtained a master’s in Molecular Biophysics from King’s College London and a Chemistry degree from University of Barcelona. She has also conducted research stays at Imperial College London and KU Leuven (Belgium). Additionally, she collaborates with several science outreach and science communication initiatives.

Title of Talk: A Universal Signature in the Melting of Metallic Nanoparticles

Abstract: Predicting when phase changes occur in nanoparticles is fundamental for designing the next generation of devices suitable for catalysis, biomedicine, optics, chemical sensing, and electronic circuits. Nevertheless, a standard definition for melting of nanoparticles is still missing and estimating the melting temperature is challenging. We analyse the solid–liquid change of several late-transition metals nanoparticles, i.e. Ni, Cu, Pd, Ag, Au, and Pt, through classical molecular dynamics. We consider various initial shapes from 146 to 976 atoms, corresponding to the 1.5–4.1 nm size range, placing the nanoparticles in either a vacuum or embedded in a homogeneous environment, simulated by an implicit force-field. We discover a universal signature in the distribution of the atomic-pair distances that distinguishes the melting transition of monometallic nanoparticles. Regardless of the material, its initial shape, size, and environment, the second peak in the pair-distance distribution function disappears when the nanoparticle melts. As the pair-distance distribution is a measurable quantity, the proposed criterion holds for both numerical and experimental investigations. Therefore, opening new experimental routes alternative to calorimetry to measure the phase change temperature. This criterion is particularly advantageous for systems whose heat capacity vs. temperature curves are of difficult interpretation, as it is the case of nanoparticles embedded in a strongly interacting environment.

DR. SREETAMA PAL (on twitter @epis_tama)

Biography: Sreetama Pal is a physical chemist fascinated by the world of cellular membranes and believes that membranes represent the one ring that binds them all. Her

doctoral research involved the identification of molecular factors that could tune the

interaction of peptides with lipid constituents of biological membranes. Her proudest

lockdown moment happened on May 29, 2020, when she defended a Ph.D. in

membrane biophysics based on her work in the Chattopadhyay laboratory at the

Centre for Cellular & Molecular Biology, Hyderabad, India. She is committed to

highlighting and supporting diversity and inclusiveness in science.

Title of Talk: When Flanking Amino Acids Flock Together: Near-Neighbor Interactions Tune Tryptophan Sensitivity to Phospholipid Headgroup Charge in Hydrophobic Peptides

Abstract: Biological membranes are bilayer assemblies of amphiphilic lipid molecules and membrane proteins that act as responsive catalytic scaffolds for numerous physiological processes mediated by membrane proteins. The aromatic amino acid tryptophan is recognized for its role in supporting the insertion, topology and function of various membrane peptides and proteins, that are central to many such cellular processes. Much of the biological relevance of tryptophans is linked to its unique chemical composition and physical properties, that translate to a preference of this amino acid for the spatiotemporally heterogeneous membrane-water interface. The interfacial localization of tryptophan residues is characterized by restricted dynamics of water molecules in its immediate microenvironment. Interestingly, this restricted solvation dynamics of tryptophan is believed to contribute to the biological role of tryptophan in membrane protein function. Here, we utilize the WALP class of α-helical synthetic transmembrane peptides to explore the modulation of tryptophan solvation dynamics by factors that mimic the physiological milieu experienced by tryptophan residues in integral membrane proteins. These factors include changes in lipid headgroup charge (known to be associated with biological processes ranging from signaling to cell death) and interactions with non-aromatic amino acids often encountered at the biological membrane-water interface. Utilizing the fluorescence-based red edge excitation shift (REES) approach, we show that the presence of flanking lysine/glycine residues impose greater restriction on tryptophan solvation dynamics, relative to that in WALP analogs with only tryptophan residues at the interface. Interestingly, the presence of these flanking residues appears to diminish the sensitivity of tryptophan residues to changes in lipid headgroup charge. These observations highlight the presence of novel regulatory mechanisms at the membrane interface that could tune the responsiveness of membrane proteins to changes in their local environment and, in a broader context, enhance our understanding of the organization, dynamics and biological relevance of aromatic amino acids.

DR. TIMOTHY DREIER (on twitter @NotHF)

Biography: After a brief stint in banking and an undergraduate Chemistry BSc. at the University of Texas – San Antonio as a non-traditional student, Tim Dreier did his doctoral work at Colorado State University. His dissertation investigated the mechanism of the Brust-Schiffrin reaction. After defending in 2017 he spent 2.5 years at Los Alamos National Lab working on gold nanoparticle polymer composite materials. Since 2019 he has been a postdoctoral researcher at the Center for Integrated Nanotechnologies at Sandia National Lab working on synthetic methodology for ferrite nanomaterials and nanomaterial composites.

Title of Talk: Synthesis & Characterization of Ferrite Nanomaterials

Abstract: Superparamagnetic nanoparticles – magnetic nanoparticles in which there is a single magnetic domain for the entire particle – have emerging applications in medical theranostics, high efficiency electronics, and EM damping. Since the early 2000s the standard synthesis of superparamagnetic nanoparticles has been a two-step process involving isolation of badly characterized intermediates followed by prolonged heating in high boiling solvent. While scalable and typically high yielding, these procedures suffer from batch-to-batch size inconsistency. Given that magnetic properties of interest scale exponentially with particle volume, fine control of size and predictable reaction outcomes are necessary to fully realize the potential of superparamagnetic nanomaterials. Herein I will discuss the fundamentals of ferrite superparamagnetic nanoparticles, their synthesis, and my recent efforts to develop robust, predictable, and tunable syntheses that are also procedurally simple and high yielding.

SAND#: SAND2021-1013 A This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. DOE’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. DOE or the United States Government.

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