Quantification of cooperativity in the self-assembly of H-bonded rosettes

The Use of the Statistical Entropy in Some New Approaches for the Description of Biosystems

Some problems of describing biological systems with the use of entropy as a measure of the complexity of these systems are considered. Entropy is studied both for the organism as a whole and for its parts down to the molecular level. Correlation of actions of various parts of the whole organism, intercellular interactions and control, as well as cooperativity on the microlevel lead to a more complex structure and lower statistical entropy. For a multicellular organism, entropy is much lower than entropy for the same mass of a colony of unicellular organisms. Cooperativity always reduces the entropy of the system; a simple example of ligand binding to a macromolecule carrying two reaction centers shows how entropy is consistent with the ambiguity of the result in the Bernoulli test scheme. Particular attention is paid to the qualitative and quantitative relationship between the entropy of the system and the cooperativity of ligand binding to macromolecules. A kinetic model of metabolism. corresponding to Schrödinger's concept of the maintenance biosystems by "negentropy feeding", is proposed. This model allows calculating the nonequilibrium local entropy and comparing it with the local equilibrium entropy inherent in non-living matter.

Stimuli-Responsive Self-Sorting Hybrid Hydrogen-Bonded/Metal-Coordinated Cage

The self-assembly of a unique molecular container is reported: a hybrid hydrogen-bonded/metal-coordinated cage where both hydrogen-bonding and metal-coordination form the crucial part of the topology. The hybrid cage was prepared combining hydrogen-bonded rosette motif and palladium(II)/platinum(II) coordination to a pyridine ligand. It was also shown that the hybrid cage could be prepared by integrative self-sorting from simple components. For the first time the genuine dual character of the hybrid cage was manifested as both self-assembling parts responded selectively to different stimuli (such as phosphine and cyanurate), which resulted in the disassembly of the cage.

Synthesis and self-aggregated nanostructures of hydrogen-bonding polydimethylsiloxane

Reversible lamellae (LAM), hexagonally packed cylinders (HPC), body-centered cubic spheres (BCC) and disordered micelles (DIM), are realized by tuning the nature of H-bonding moieties (Ba, TAP, HW), the molecular weight of PDMS, and the temperature.

Cooperative assembly of H-bonded rosettes inside a porphyrin nanoring

The melamine·barbiturate H-bonded rosette motif is of comparable dimensions and symmetry to the cavity of a butadiyne-linked 6-porphyrin nanoring. Functionalisation of each of the barbiturate components and the pyrimidine components of a H-bonded rosette with a pyridine ligand leads to a self-assembled hexapyridine ligand, which binds cooperatively to the zinc porphyrin nanoring. UV-vis-NIR and ¹H NMR experiments show that the 7-component assembly forms at concentrations at which neither the H-bonding interactions nor the zinc porphyrin–pyridine interactions are formed in the absence of one of the three components. The mean effective molarities of these rosette complexes are around 200 mM in chloroform at 298 K.

Mixing barbiturates and pyrimidines equipped with pyridine ligands to leads to self-assembly of a hexadentate rosette ligand, which is complementary to a hexameric zinc porphyrin macrocycle.