How the 4% grafting of mannobiose alters the properties of the polyelectrolyte, linear polyethylenimine (PEI), which has protonable amines and is used widely for complexing DNA, is investigated. The pH‐dependence of the PEI charge, zeta potential, and hydrodynamic radius changes when the polymer charge increases beyond 50–60%. According to MD simulations, this transition in pH‐ or charge‐ dependence is a short‐range structural response to amine protonation (i.e., change in intrinsic persistence length) rather than a longer‐range charge‐repulsion response. Upon mannobiosylation, the 50% charge state of PEI shifts from ≈pH 6 toward ≈pH 4. The protonability of PEI is lowered and restricted to limited charge states. These mannobiosylation‐induced shifts are reversed by salt and uncharged chaotropes, indicating that hydrogen‐bonding interactions fostered by the grafted sugars are lowering the protonation pKa of PEI. These findings have broad implications for the analytical modeling of polyelectrolytes, the design of PEI‐based gene‐delivery systems, and for understanding how oligosaccharides modify cell and protein surfaces.

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The recent observation of the explosive oxidation of graphene with enhancement for decreasing temperature and the requirements for synchronizing oxidants for collective oxidation-reduction (redox) reactions presented a chemical scenario for the thermal harvesting by the magnetic spin Hall Effect. More experimental data are presented to demonstrate such spin Hall Effect by determining the influence of spins of so-called spectator fermionic cations. Furthermore, the so-called spectator bosonic cations are discovered to cause a Klein tunneling effect during the redox reaction of graphene. The Na(+) and K(+), fermionic cations and the Mg(2+) and Ca(2+), bosonic cations were observed and compared under a variety of experimental conditions: adiabatic reactions with initial temperatures (18-22 °C); reactions toward infinite dilution; isothermal reactions under nonadiabatic conditions at low temperature of 18 °C; reactions under paramagnetic O(2) or diamagnetic N(2) atmospheres of different permeabilities; reactions in applied and no applied external magnetic field; and reactions toward excess concentrations of common and uncommon Na(+) and Mg(2+) cations. The observed reaction kinetics and dynamics under these various, diverse conditions are consistent with the spin Hall mechanism, energy harvesting and short time violation of Second Law of Thermodynamics for redox reactions of graphene by the Na(+)K(+) mixture and are consistent with the Klein tunnel mechanism for the redox reactions of graphene by the Mg(2+)Ca(2+) mixture. Mixed spin Hall and Klein tunnel mechanisms are discovered to slow and modulate explosive redox reactions. Such spin Hall Effect also gives explanation of recent tunneling of electrons through boron nitride.

Nucleic acid probes are used for diverse applications in vitro, in situ, and in vivo. In any setting, their power is limited by imperfect selectivity (binding of undesired targets) and incomplete affinity (binding is reversible, and not all desired targets are bound). These difficulties are fundamental, stemming from reliance on base pairing alone to provide both selectivity and affinity. Shielded covalent (SC) probes eliminate the longstanding trade-off between selectivity and durable target capture, achieving selectivity via programmable molecular conformation change and durable target capture via activatable covalent cross-linking (Vieregg et al, J. Am. Chem. Soc. 2013). In pure and mixed samples, SC probes covalently capture complementary DNA or RNA oligonucleotide targets and reject two-nucleotide mismatched targets with near-quantitative yields at room temperature, achieving discrimination ratios of 2À3 orders of magnitude. Semi-quantitative studies with full-length mRNA targets demonstrate selective covalent capture comparable to that for RNA oligo targets. Single-nucleotide DNA or RNA mismatches, including nearly isoenergetic RNA wobble pairs, can be efficiently rejected with discrimination ratios of 1À2 orders of magnitude. Covalent capture yields appear consistent with the thermodynamics of probe/target hybridization, facilitating rational probe design. If desired, cross-links can be reversed to release the target after capture. In contrast to existing probe chemistries, SC probes achieve the high sequence selectivity of a structured probe, yet durably retain their targets even under denaturing conditions. This previously incompatible combination of properties suggests diverse applications in vitro and in vivo; this talk will present our latest results on SC probe applications.