Multiscale Origami Structures as Interface for Cells

A DNA‐based platform was developed to address fundamental aspects of early stages of cell signaling in living cells. By site‐directed sorting of differently encoded, protein‐decorated DNA origami structures on DNA microarrays, we combine the advantages of the bottom‐up self‐assembly of protein–DNA nanostructures and top‐down micropatterning of solid surfaces to create multiscale origami structures as interface for cells (MOSAIC). In a proof‐of‐principle, we use this technology to analyze the activation of epidermal growth factor (EGF) receptors in living MCF7 cells using DNA origami structures decorated on their surface with distinctive nanoscale arrangements of EGF ligand entities. MOSAIC holds the potential to present to adhered cells well‐defined arrangements of ligands with full control over their number, stoichiometry, and precise nanoscale orientation. It therefore promises novel applications in the life sciences, which cannot be tackled by conventional technologies.     

Undergraduate women empowering women in computational chemistry: Three perspectives

The undergraduate computational chemistry research group headed by Mauricio Cafiero at Rhodes College has a history of including, promoting, and supporting women in this predominantly male field. Alums of this research group from 2004 to 2019 include nine M.Ds, two science researchers, two Ph.D.s, one secondary teacher, two pharmacists, a physical therapist, two nurses, six current medical school students, and five current science graduate students. They have produced 18 peer-reviewed publications with female undergraduate first authors and over 100 conference presentations, including 9 international conference presentations. While Professor Cafiero does all he can to support these students, he attributes the continuous success of the group in recruiting, retaining, and supporting these women to the students themselves. The students' success and visibility on campus helps to recruit new students. The heavy presence of women in this group provides a strong support system for women who may otherwise feel isolated in a male-dominated field; and these support groups provide models and support for women to overcome common obstacles that women in science face. We will profile three recent graduates who will discuss how the above points affected them during their time in the research group and discuss their experience in the context of some literature on women in Science, Technology, Engineering and Mathematics.     

Palladium-catalyzed C-H perfluoroalkylation of arenes

A new Pd-catalyzed reaction for the coupling between perfluoroalkyl iodides (R(F)I) and simple aromatic substrates is described. The perfluoroalkylated arene products are obtained in good to excellent yields in the presence of a phosphine-ligated Pd catalyst and Cs(2)CO(3) as a base. The development, optimization, scope, and preliminary mechanistic studies of these transformations are reported.     

Understanding the impact of the P-loop conformation on kinase selectivity

This work addresses the link between selectivity and an unusual, folded conformation for the P-loop observed initially for MAP4K4 and subsequently for other kinases. Statistical and computational analyses of our crystal structure database demonstrate that inhibitors that induce the P-loop folded conformation tend to be more selective, especially if they take advantage of this specific conformation by interacting more favorably with a conserved Tyr or Phe residue from the P-loop.     

Resorcinol-templated synthesis of a cofacial terpyridine in crystalline π-stacked columns

A resorcinol achieves a templated stereospecific and near-quantitative synthesis of a cofacial terpyridine in the solid state. The solid-state synthesis occurs in one-dimensional π-stacked columns with reactivities highly sensitive to peripheral groups attached to the template.     

1,N6‐Etheno‐2′‐deoxytubercidin hemihydrate

The title compound [systematic name: 7‐(2‐deoxy‐β‐d ‐erythro‐pentofuranosyl)‐7H‐imidazo[1,2‐c]pyrrolo[2,3‐d]pyrimidine hemihydrate], 2C₁₃H₁₄N₄O₃·H₂O or (I)·0.5H₂O, shows two similar conformations in the asymmetric unit. These two conformers are connected through one water molecule by hydrogen bonds. The N‐glycosylic bonds of both conformers show an almost identical anti conformation with χ = −107.7 (2)° for conformer (I‐1) and −107.0 (2)° for conformer (I‐2). The sugar moiety adopts an unusual N‐type (C3′‐endo) sugar pucker for 2′‐deoxyribonucleosides, with P = 36.8 (2)° and τ_m = 40.6 (1)° for conformer (I‐1), and P = 34.5 (2)° and τ_m = 41.4 (1)° for conformer (I‐2). Both conformers and the solvent molecule participate in the formation of a three‐dimensional pattern with a `chain'‐like arrangement of the conformers. The structure is stabilized by intermolecular O—H...O and O—H...N hydrogen bonds, together with weak C—H...O contacts.     

Maximising entropy on the nonparametric predictive inference model for multinomial data

The combination of mathematical models and uncertainty measures can be applied in the area of data mining for diverse objectives with as final aim to support decision making. The maximum entropy function is an excellent measure of uncertainty when the information is represented by a mathematical model based on imprecise probabilities. In this paper, we present algorithms to obtain the maximum entropy value when the information available is represented by a new model based on imprecise probabilities: the nonparametric predictive inference model for multinomial data (NPI-M), which represents a type of entropy-linear program. To reduce the complexity of the model, we prove that the NPI-M lower and upper probabilities for any general event can be expressed as a combination of the lower and upper probabilities for the singleton events, and that this model can not be associated with a closed polyhedral set of probabilities. An algorithm to obtain the maximum entropy probability distribution on the set associated with NPI-M is presented. We also consider a model which uses the closed and convex set of probability distributions generated by the NPI-M singleton probabilities, a closed polyhedral set. We call this model A-NPI-M. A-NPI-M can be seen as an approximation of NPI-M, this approximation being simpler to use because it is not necessary to consider the set of constraints associated with the exact model.     

Energetics of lysozyme adsorption on mesostructured cellular foam silica: effect of salt concentration

The heat of lysozyme adsorption on mesostructured cellular foam (MCF) silica was measured using flow microcalorimetry (FMC) to investigate the influence of a neutral salt, sodium sulfate. At concentrations up to 0.5 M sodium sulfate, a complex initial exotherm was followed by an endotherm. Protein surface coverage, the magnitudes of the exothermic heat signals and the magnitudes of the net heat of adsorption increased with sodium sulfate concentration. These observations suggest that electrostatic interactions are the principal driving force at low ionic strengths; van der Waals interactions become dominant at higher salt concentrations. Each exotherm could be deconvoluted into two exotherms, indicating multiple modes of lysozyme attachment to the silica surface. The endothermic peak, associated with protein desorption, disappeared at the highest sodium sulfate concentration (1.0 M), indicating irreversible adsorption of the protein on the MCF silica surface. The data are consistent with an adsorption mechanism in which the initial attachment of lysozyme to the surface is followed by a reorientation and formation of a secondary or stronger attachment to the surface.