Immobilization of surface non-affinitive protein onto a metal surface by an external electric field.

We investigated an alternate technique to coat the surface with a protein having no surface affinity, without the use of any exotic chemical agents. An external electric field was utilized to prepare the protein coating on a metal substrate. Stainless steel (St) substrate and lysozyme (LSZ) were used as the surface to be coated and the model non-adsorptive protein, respectively. Dynamics of the adsorption of LSZ on the St surface in the presence and absence of an external electric potential (EEP) were monitored by in-situ ellipsometry. Applying negative surface potential (-0.4 V vs Ag/AgCl) forced the adsorption of LSZ onto the St surface where LSZ did not adsorb without applying any EEP. The repetition of the EEP-application and -cut-off indicated the controllability of the LSZ coating amount depending on the total duration of the EEP-application. The coated LSZ largely remained bound to the surface even by the cut-off of the external electric field, the ratio of which to the detached amount was roughly constant (approximately 7:3). Furthermore, the LSZ coated surface on the St substrate was found to be reversibly switched between being affinitive and non-affinitive to a typical model protein adsorbate (bovine serum albumin) by the EEP-application and cut-off.

Molecular recognition in curved π-systems: effects of π-lengthening of tubular molecules on thermodynamics and structures.

The thermodynamics and molecular structure of a supramolecular complex between a tubular molecule, (P)-(12,8)-[4]cyclo-2,8-anthanthrenylene, and fullerene were investigated. The enthalpy-driven characteristics of the association were enhanced upon lengthening of the curved sp2-carbon networks in the tubular molecule as a result of an increase in the C-C contact areas in addition to the emergence of CH-π contacts with aliphatic chains. The involvement of CH-π interactions in the molecular recognition consequently increased the entropy cost for the association, and the importance of molecular structures at the edge of tubular molecules was revealed. An inflection-free, smooth surface inside the tubular molecule was revealed by crystallographic analysis, which allowed for dynamic motions of the encapsulated fullerene molecule in solution. This study provided a new example of a molecular peapod with a smoothly curved π-interface to be examined in the structure-thermodynamics relationship study and led to an in-depth understanding of peapods in general.

Photoinduced electron transfer in a dynamic supramolecular system with curved π-structures.

Photoinduced electron-transfer processes in a carbonaceous supramolecular combination of a tubular host and a C60 guest were investigated with time-resolved transient absorption spectra upon laser flash photolysis. Following the formation of triplet charge-separated species via electron transfer from the host to the guest, a rapid back electron transfer proceeded to afford triplet C60.

Asymmetric autocatalysis initiated by finite single-wall carbon nanotube molecules with helical chirality.

An asymmetric autocatalysis reaction was initiated by a finite single-wall carbon nanotube molecule with helical chirality. The asymmetric induction was initiated by the chiral environment arising from the planar chirality of the tubular polyaromatic hydrocarbons.

Assessment of fullerene derivatives as rolling journals in a finite carbon nanotube bearing.

Conformance assessment of rolling journals in a molecular bearing has been carried out with a combination of fullerenes and finite single-wall carbon nanotube molecules through quantitative analysis of the binding affinities. Endohedral fullerenes were applicable to three-body molecular bearings with slightly weaker binding affinities. Exohedral shaft moieties on C60 journals affected the binding affinities to reduce the binding constants to a considerable extent, and oval-spherical C70 journals were superior in tolerating bulky shaft attachments.