CPA - Postdoc Launch Seminar 2026 - II
Dear Postdocs,
We have another Caltech Postdocs Launch seminar this Friday!
We'll have two wonderful talks from Dr. Vignesh Ravichandran (BBE) and Dr. Sabrina Wahler (CCE), whose titles and abstracts can be found below.
And as always - FREE Lunch and beverages will be there before the talks start. To make sure we can order enough food, please RSVP here beforehand: https://forms.gle/T6M8g3FfWVk8ZF2q6
What – Caltech Postdocs Launch
When – Friday, 26th of June, 2026, 11:45 AM
Where – Chen 130
Hope to see you there!
Best wishes,
Postdoc Launch Team
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Un-FROG-ettable Fluorescence
Dr. Vignesh Ravichandran
The vivid green coloration of arboreal frogs, crucial for their camouflage, represents a fascinating case of evolutionary innovation in optical biology. Unlike most amphibians that rely on chromatophore arrangements, the Neotropical treefrogs achieve leaf-mimicking coloration through sequestering biliverdin (BV, a blood-derived pigment) via serpin-family proteins. Biliverdin binding serpins (BBSs) of Hylid and Centrolenid treefrogs binds BV with remarkable high affinity, fundamentally altering the spectral properties of BV to resemble plant chlorophyll. Using hyperspectral photoacoustic tomography, we reveal that BBSs are distributed systemically, contributing to whole-body camouflage rather than localized pigmentation. Importantly, these proteins contribute to interspecific variation in color saturation and hue — suggesting fine-tuned evolutionary optimization of the biliverdin-binding pocket. This work also reveals an unexpected functional property: BBSs emit near-infrared fluorescence (>700 nm) in a biological transparency window. By examining ancestral serpin sequences and the evolutionary expansion of the biliverdin-binding pocket, we illuminate serpin evolution, protein thermostability, and the potential for developing novel NIR molecular probes. We will also contextualize these findings within chlorotic frogs of Hyperolidae, Mantellidae, and Rhacophoridae, exploring convergent and divergent evolutionary strategies for achieving NIR fluorescence across amphibian families.
From Small Boom to Big Boom: Predictive Modeling of Energetic Material Performance
Dr. Sabrina Wahler
The modified Kamlet–Jacobs framework, RoseModKJ, a reparametrization of the expansion adiabat slope, allows prediction of detonation pressure as a function of relative volume along the expansion path. By reformulating the adiabat slope, RoseModKJ achieves close agreement with established thermochemical codes such as EXPLO5, as well as with experimental data and first-principles simulations based on ReaxFF and QM-MD. A key advantage of this approach is its ability to reconstruct full expansion adiabats directly from elemental composition and initial density - without requiring heats of formation. This enables rapid, physically grounded estimates of detonation behavior, including the region near the Chapman–Jouguet (CJ) point, where detonation velocity, pressure, and temperature are defined. Importantly, the way detonation gases expand determines how energy is transferred to the surroundings: it controls how strongly materials are accelerated in propulsion and ballistic systems and how blast waves propagate through air. As a result, accurate prediction of the expansion behavior is essential both for designing high-performance energetic materials and for estimating safety distances in hazard scenarios. Overall, RoseModKJ provides a fast and robust framework for exploring detonation thermodynamics, making it well suited for the screening and rational design of new energetic materials, while also offering insight into the underlying physics of expansion processes.