Sunday, March 24, 2019

Using dice, fuzzy or not, to move molecules

This post has been a long tine coming... I wrote it back in May 2015, and somehow in the middle of things, I forgot to hit "publish." While we have done quite a bit of work with this model since then, maybe you'll still enjoy our crazy analogy to playing dice with particles at the mesoscale...

Some time ago, I published what might seem as yet another paper describing the properties of our model for (coarse-grained) large-scale macromolecules. A critical part of the model is that we roll dice every time these particles collide so as to decide whether they bounce or go through each other. They can overlap, because at intermediate length scales, they don't behave like rocks even if they occupy space. Despite our simple (and dicey) model, in our earlier papers, we showed that our particles give rise to the same structure as the corresponding particles that would interact through typical (so-called soft) interactions. But Einstein's famous quote about God not playing dice with the universe (albeit in a different context) serves as a warning that our particles might not move in analogous ways to those driven by Newton's deterministic laws. In our most recent paper, we confirmed that our particles (if they live in one dimension) do recover deterministic dynamics at sufficiently long (that is, coarse-grained) length scales. That's a baby step towards using our model in human-scale (three) dimensions. So there are more papers to come!

The work was performed (and the paper was written) with my recent Ph.D. graduate, Dr. Galen Craven, and a Research Scientist, Dr. Alex Popov. It's basic research and I'm happy to say that It was supported by the National Science Foundation. The title of the article is "Stochastic dynamics of penetrable rods in one dimension: Entangled dynamics and transport properties," and it was recently published at J. Chem. Phys. 142, 154906 (2015).

Sunday, March 17, 2019

Engineered gold nanoparticles can be like ice cream scoops covered in chocolate sprinkles

There are many ways to interrogate molecular phenomenon. You might think that this is restricted to physical measurements such as direct observation with a microscope, a laser, or more seemingly arcane observation with nuclear magnetic resonance (NMR). But I’m happy to report that observation of computer simulations is yet another, as long as our models are sufficiently accurate that they mimic reality perfectly. In today’s age when it’s hard to see the difference between CGI and real humans, this may not sound surprising. Nevertheless, the question is what can we learn from observation of real and simulated systems in tandem?

I’m happy to report that my student Gene Chong and Cathy Murphy’s student Meng Wu did precisely this parallel study. Gene made simulations of a simpler system, involving nanoparticles covered by lipids called MUTABs. Meng made NMR measurements of nanoparticles covered by a similar but somewhat longer lipids called MTABs. (Note that if you are worried about the term nuclear in NMR, as in nuclear energy, don’t be. We are just looking at the positions of the nuclei, not spitting them apart. It was the concern over this misunderstanding that led to the use of such a device to look at your body in detail to be called MRI instead of NMR!) The happy result was that the two observations agreed. But only together did Meng’s and Gene’s observations show clearly that the lipids didn’t always cover the nanoparticle smoothly like melted chocolate on ice cream, but rather assembled like sprinkles all pointing out in the same direction packed together in different islands on the surface. This structure means that lipid-decorated nanoparticles will have shape and response to other systems that you might not otherwise anticipate. And this opens the question to our next set of investigations as we chart a course to understand the interactions between nanoparticles and biological components such as membranes.

If you want more detail, check out our article in JACS, just recently published!  That is, JACS 141, 4316 (2019), and I'm happy to report that it was funded by the NSF CCI program for our Center for Sustainable Nanotechnology.

Tuesday, March 5, 2019

Deleted edits from my Comment on diversity and inclusion

When writing a Comment in any magazine, you invariably have a word limit. It's also important to stay on message so that readers won't get lost in the weeds. Thankfully, C&EN has great editors, and it was a pleasure to work with them to write my recent Comment (details at bottom) to help me stay on message. Indeed, while I appreciate the power of blogging and writing unfettered, there is great value in a strong editor. I am thankful that we still have them in the publishing world. In case, though, you want to see some of the weeds that got cut out, here's your sneak peak:

"An evocative triple or triad for managing diversity and advancing inclusive excellence is Support. Compliance, and Adjudication."

"Compliance is necessary in today’s world because we have seen that without it, systems tend to move out of whack, but it tends to be seen to be about protecting an administration from legal attacks."

"Adjudication provides a mechanism to resolve conflicts between aggrieved parties, but who decides which party is in the right or wrong, and how can we be sure that they are fully supporting the individuals fairly."

"Does a member trust us an authoritative source of information? Does a member trust us to prepare them throughout their professional career progression? Does a member trust us even when we tell them that they are wrong? If we are to foster a healthy diversity culture within our Society, we need to be able to do all of this while still being a single organization."

"This [a workshop held at Barnard] included 1-point gains on a 5-point scale on four of the six objectives: (1) the difference and importance of transactional solutions vs. policy solutions as it pertains to managing diversity equity and inclusion, (2)  factors for administering recruitment, mentoring, tenure and promotion processes that advance inclusive excellence, (3) evidence-based strategies for addressing known barriers within a department so as to reduce existing diversity inequities, and (4) supporting and communicating inclusive excellence. Our targeted learning outcomes clearly resonate with the three legs of our managing diversity table and our approach to managing them. "

"The perhaps surprising outcome is that the practices necessary to manage diversity are simply the applications of good management to achieve a targeted outcome, which in this case is inclusive excellence."

"The courses offered by the ACS through the Leadership Advisory Board (LAB) where essential to me as I have developed as a leader, and I’m happy to recommend then to you so as to learn the underlying principles of management."

I also hope that you have a chance to read my recent Comment in C&EN on "Bringing diversity and inclusion to the ACS table." (Volume 97, Issue 9, March 2, 2019) If not, please check it out. Access is free if you are an ACS member. Otherwise, you can use one of your 5 free monthly views... And if you are a chemist, please consider joining.