Influence of nanohelical shape and periodicity on stem cell fate.

Microenvironments such as protein composition, physical features, geometry, and elasticity play important roles in stem cell lineage specification. The components of the extracellular matrix are known to subsequently assemble into fibrillar networks in vivo with defined periodicity. However, the effect of the most critical parameter, which involves the periodicity of these fibrillar networks, on the stem cell fate is not yet investigated.

Counteranion effect on micellization of cationic gemini surfactants 14-2-14: Hofmeister and other counterions.

The effect of counterions was investigated and analyzed to probe the principal ionic effects influencing the micellization behavior of dimeric cationic surfactant ethanediylbis(dimethyltetradecylammonium), referred to as gemini 14-2-14. The 30 counterions were classified to four different families depending on their nature: (1) small and inorganic counterions which are typically taken from the Hofmeister series were studied to focus on the effect of ion type; (2) n-alkyl carboxylate counterions were studied to focus on the effect of the hydrophobicity of counterions; (3) aromatic carboxylate counterions were included to focus on the effect of the position of substitutions; and (4) other counterions were included in order to shed light on other parameters. By investigating the critical micelle concentration (CMC), ionization degree of micelle (alpha), free energy of micellization (DeltaG(M)), and aggregation numbers N of the gemini surfactant with these different types of anions, we demonstrated the effect of different ion properties independently.

Nucleotide-promoted morphogenesis in amphiphile assemblies: kinetic control of micrometric helix formation.

Anionic nucleotides adenosine monophosphate or guanosine monophosphate interact with cationic vesicles, exchange with the counteranions of the amphiphiles in situ, and organize themselves at the membrane surfaces. Such organized nucleotides reciprocally transfer their chirality to membranes of nonchiral amphiphiles to induce the formation of right-handed micrometric helices on the time scale of hours. The kinetics of the nucleotide molecular organization and the formation of supramolecular helices was followed.