Research Highlights

Graphical Abstract Article Topic Summary
Plant wall

Solid-State NMR Views of Plant Cell Walls and Mutants

In two recent publications, solid-state NMR and Dynamic Nuclear Polarization (DNP) techniques were used to characterize the structure of Arabidopsis and two allelic mutants for a pectin methyltranferase and the cell wall structure of wild-type and mutant rice stems without isotopic labeling.  Kirui et al. | Zhao et al.
Reaction-diffusion hydrogels from urease enzyme particles

Reaction-diffusion hydrogels from urease enzyme particles

Inspired by biofilm formation, we present a general method for the growth of hydrogels from urease enzyme-particles by combining production of ammonia with a pH-regulated polymerization reaction in solution. This approach can be exploited to create enzyme-hydrogels or chemically patterned coatings for applications in biocatalytic flow reactors. Mai et al. 
Synthesis of a nitrogenase assembly protein 

EPR-MCD study reveals unexpected synthesis of a nitrogenase assembly protein 

NifB, a radical SAM enzyme, catalyzes the biosynthesis of the L cluster, a structural homolog and precursor to the nitrogenase active site MoFe7S9C·R-homocitrat. We report a VTVH MCD/EPR spectroscopic study of the initial interaction of SAM with [Fe4S4]SAM in  a variant NifB protein (MaNifBSAM). It reveals that [Fe4S4]SAM exists in two forms, which are involved in the synthesis of the L cluster. Rupnik et al. 
Radical induced cationic frontal polymerization

Radical-induced cationic frontal polymerization

Vinyl ethers are highly reactive monomers desired in coatings for their fast curing, low toxicity, and good adhesion. The kinetic effects of vinyl ether addition to epoxy systems were studied using radical-induced cationic frontal polymerization, which used an initiator system comprised of a superacid-generating iodonium salt and a peroxide thermal radical initiator. Results showed that increase of divinyl ethers increased the front speed, as did increase in concentration of the initiator system, while hydroxymonovinyl ethers negatively affected frontal polymerization. Groce et al. 
Development of adhesive microfluidic gradient generator Development of adhesive microfluidic gradient generator Microfluidic gradient generators have been used to study cellular migration, growth, and drug response in numerous biological systems. One common device combination is Polydimethylsiloxane (PDMS)/ Agarose hydrogel system however, there is no adhesive interaction between PDMS and agarose layers therefore experiment gets complicated and fails often. In this work, a two-layer, flow-free microfluidic gradient generator was developed using thiol-ene chemistry. Both of these layers bind quickly and strongly when they are brought together which eliminates the major issue with conventional flow-free gradient generators. Khan et al.
Metallatetrahedrane intermediates in alkyne metathesis Metallatetrahedrane intermediates in alkyne metathesis Alkyne metathesis typically operates through a metallacyclobutadiene intermediate. On the other hand, metalltetrahedranes are commonly considered as off-cycle byproducts that interfere with the reaction. The Lee group recently isolated a Mo(VI)-metallatetrahedrane that was catalytically active. Here, they investigate the factors that determine the formation of metallatetradedranes and how they affect the alkyne metathesis mechanism. [Funded by the National Science Foundation under grant 1956302] Thompson et al.
Influence of NaCl on shape deformation of polymersomes Sodium Chloride induced shape deformations of polymersomes NaCl induced shape deformations of polymersomes composed of amphiphilic triblock copolymers were analyzed using Small Angle Neutron and X-ray Scattering. Spherical polymersomes transform from spherical to multi-vesicular structures with increasing salt concentrations. While the membrane thickness shows an initial decrease and then a gradual increase, the inter-layer water thickness decreased until a constant value is reached. [DOE Open Access on 3/2022]  Perera et al. 
Self-assembly of peptoid polymers Self-Assembly of peptoid polymers The intermolecular interactions amongst the peptoid polymers can be fine-tuned by controlling the N-substituent sidechain structures. In this study, branching pattern of peptoid polymer sidechains have been shown to effectively modulate the molecular shape of entire polymer chains and the collective assembly of polymers in solution to form two- or three-dimensional hierarchical structures. [Funded by the National Science Foundation under grant 1609447]  Kang et al. 
nickel complex with helical shape New nickel complexes have helical shape Together with Prof. Uttam Pokharel (Nicholls State University), we prepared six new nickel complexes with organic ligands, which fold and twist into helical shapes. The center of these complexes, between the two nickel atoms, is like a nano-scale “box”, but it’s empty. However, we are now designing complexes that will have room for other molecules to fit in the box. Then, we may be able to use them to transport molecules or ions from one place to another. Pokharel et al. 
Graphics of bottlebrush polymer relaxation times Relaxation Behavior of Bottlebrush Polymers The segmental relaxation times of different bottlebrush polymer have been investigated by dielectric spectroscopy and compared to their linear counterparts. Depending on the side chain length, a slowed down process can be observed which levels out for bottlebrush polymers having sufficiently long side chains. [Funded by the U.S. Department of Energy (DoE) under grant DE-SC0019050]  Bottlebrush Polymer Article >
Sythesis of well-defined polypeptoid mimics of pily(glutamic acid) Synthesis of well-defined polypeptoid mimics of poly(glutamic acid) N-(3-tert-butoxy-3-oxopropyl) glycine derived N-carboxyanhydride was successfully synthesized and polymerized by ring-opening polymerization using primary amine initiators. The polymerization was found to proceed in a controlled manner over a wide range of molecular weights while maintaining a narrow molecular weight distribution. Mild acidic conditions readily unveil the carboxyl functionality to yield the pH-responsive, structural mimic of the biologically relevant peptide, poly(glutamic acid). Synthesis Article > 
Reducing toxic hexavalent chromium to benign Cr(III) using electrochemistry Electrochemical Reductions of Chromium(VI) in Water Reducing toxic hexavalent chromium to benign Cr(III) using electrochemistry is a promising way to purify contaminated water. To improve current methods and develop new ones, it is paramount to understand the thermodynamic and kinetic parameters of the reactions involved. Purify Water Article >
Spherical bottlebrushes in linear melt Size Changes of Spherical Bottlebrushes in Linear Melt Spherical bottlebrushes change the size depending on the molecular weight of the linear host matrix. Small-angle neutron scattering allowed to detect these changes, resulting in decreasing bottlebrush radii with increasing molecular weight of the linear host matrix. Additionally, aggregation can be observed in the largest host matrix at the highest concentration. [Funded by the U.S. Department of Energy(DoE) under grant DE-SC0019050] Bottlebrush Polymer Article >

 

Graphical Abstract Article Topic Summary
 Boron dipyrromethenes (BODIPYs) bearing multiple methyl substituents BODIPYs with Restricted Meso-8-Aryl Rotation   Boron dipyrromethenes (BODIPYs) bearing multiple methyl substituents and a meso-8-aryl group were synthesized and investigated, both experimentally and computationally. The free rotation of the meso-8-aryl group is prevented due to the presence of the 1,7-dimethyl groups and of ortho-substituents on the meso-8-aryl ring, resulting in BODIPY derivatives with high fluorescence quantum yields, independent of the solvent viscosity. BODIPY Article >
Hydrogen bond probing  Probing Weak Hydrogen Bonds with Time-Resolved Spectroscopy Weak hydrogen bonds between the highly polarized hydrogen atom of chloroform and the amide carbonyl were proved and probed via linear and nonlinear IR spectroscopic techniques. Experiments showed that weak hydrogen bonds have an energetics of few kcal/mol and are responsible for distinguishable arrangements of chloroform molecules around carbonyl groups. Hydrogen Bonds Article > 
Thermal effect on frontal polymerization Thermal and Chemical Effects of Fillers on Free-Radical Frontal Polymerization Filled systems are important for the development of materials through frontal polymerization. Fillers are added to control the rheological properties of the formulation and to enhance the mechanical properties of products. Results demonstrate that some fillers can increase front velocity through their high thermal diffusivities while others decrease it by acting as radical scavengers. Frontal Polymerization Article > 
Engineered Soil Utilizing Engineered Soil Surrogates to Study Environmental, Ecological, and Agricultural Processes A novel model approach was developed and applied to gain a molecular-level understanding of environmental pollutant/soil interactions. The approach provides a scalable platform with molecular-level control of the soil organic matter (SOM) chemical composition and structure, allowing one to examine proposed SOM interactions with agricultural chemicals and beyond. [Open Access Article]
Reducing Toxic Hexavalent Chromium in Water Reducing Toxic Hexavalent Chromium for Clean Water Highly toxic Cr(VI) can be reduced to benign Cr(III) in water on unmodified and inexpensive carbon electrodes. The slow step over a wide range of pH is identified, which will help develop new energy-efficient water purification technologies. Clean Water Article >
Tunable surface properties for microfluids Tunable Surface Properties for Microfluidics Prepared with Simple, Thiol-acrylate Chemistry Novel, cost-efficient bulk modified thiol-acrylate microfluidic materials with wide range of highly stable hydrophilic surfaces (11° to 85°) prepared without expensive and sophisticated techniques within less than 24 h at room temperature and ambient pressure. Microfluidic Article >
Frontal Polumerization affecting surface Frontal Polymerization The capacity of frontal polymerization as a coating strategy for wood substrates was studied. Results indicate resin viscosity and film thickness critically affect the qualitative and quantitative propagation of the thermal front resulting in the formation of the coating. Frontal Polymerization Article >
Hydroformylation structure of Cationic Cobalt(II) Cationic Cobalt(II) Bisphosphine Hydroformylation Catalyst Hydroformylation is one of the highest-volume homogeneously catalyzed industrial processes today. One segment of the market deals with unreactive alkenes that require the most active cobalt or rhodium-based catalysts that need high pressures (> 200 atm) to prevent decomposition of the catalysts. A new class of cationic cobalt bisphosphine hydroformylation catalysts exhibit exceptional activity under medium pressure conditions and remarkable stability with respect to cobalt-induced phosphine degradation reactions or decomposition to cobalt metal. Hydroformylation Article >
STEM Diversity Research and Training Program A multiple case study involving participants of an MRT program who completed a BSc degree but did not subsequently matriculate into a doctoral program. Results identify perceived barriers deterring continuation into doctoral degree programs among former MRT participants. MRT Article >
The kinetics of photopolymerization in deep eutectic solvents (DESs) is investigated through RT‐FTIR. The Photopolymerization of Monomer-Containing Deep Eutectic Solvents The kinetics of photopolymerization in deep eutectic solvents (DESs) is investigated through RT‐FTIR. The systems of this study are choline chloride DESs made of acrylic acid and methacrylic acid (DES monomers) and a nonreactive analog isobutyric acid. Analysis of the evolution of conversion indicates dramatic increase in polymerization rate when comparing the polymerization of the DES monomers to pure monomer polymerization. Photopolymerization Article >
metallatetrahe Mᴏ(VI)- Metallatetrahedrane  A siloxide podand ligand is used to tease out structure-reactivity relationships in alkyne metathesis. It also affords a very rare (and dynamic!) metallatetrahedrane. Metallatetrahedrane Article >

 

Graphical Abstract Article Topic Summary
Electron Spin Probing Electron Spins in Enzymes Biosynthesis MCD and EPR probing of the nitrogenase M cluster precursors electron spins dynamics suggests new mechanisms of enzymes biosynthesis and substrate binding. Additional ongoing ultrafast electron-scale investigations are carried out to get better understanding of such mechanisms. Probing Electron Spins Article > 
Bodipy image Bodipy A synthesis of linker-free BODIPY-glycine derivatives, via functionalization at the boron atom, is reported. The new compounds were studied experimentally and computationally, and shown to have high stability and fluorescence quantum yields. Bodipy Article >
molecular structure of electrolytes Electrolytes in Motion The molecular structure and dynamics of electrolytes is important in science and engineering due to their use in electrochemical storage. Time resolved infrared spectroscopic methods are currently the best tools for investigating the electrolytes at the microscopic level, but understanding these liquid systems remains very challenging. Electrolytes in Motion Article >
Diversity in Sciene, Technology, Engineering, and Mathematics Diversity in STEM An evaluation study with a mixed methods approach evaluating program impacts and outcomes of a minority training program over a period of 14 years. Results indicate which strategies were most effective in promoting interest and matriculation into graduate programs among underrepresented groups in STEM. STEM Diversity Article >
image of stabilization of Electrocatalysts Stabilization of Electrocatalysts Fighting deactivation: Classical and emerging strategies for efficient stabilization of molecular electrocatalysts. Stabilization of Electrocatalysts Article >
Quorum Sensing image Quorum Sensing Quorum Sensing is a biological phenomenon of cellular communication which plays a role in biofilm development or even bacteria colony growth. We emulate this communication by using an analog of urease encapsulated beads subjected to a urea solution. Quorum Sensing Article >
Defensins in membranes image Defensins in Membranes High-resolution ¹³C, ³¹P and ¹H Solid-State NMR and 5-µs MD modeling are integrated to determine the site-specific structure of human defensins in lipid bilayers and how these peptides reshape lipid vesicles. Defensins Article >
photochemical oxidation graphical abstract Photochemical Oxidation Mass Spectrometry  A193 nm laser is directed at the electrospray source of a mass spectrometer that contains hydrogen peroxide and a protein. The photogenerated radicals oxidize the protein, enabling ultrafast characterization of its structure. Mass Spectrometry Article >
Carbon Nanohoops Image Carbon Nanohoops Carbon nanohoops are conjugated macrocycles with radially-arranged aromatic groups. Here, a carbon nanohoop was prepared in high yields from a non-symmetric building block using alkyne metathesis. This nanohoop exhibited blue fluorescence with high quantum yields. Carbon Nanohoops Article >