Molecular Recognition of Nucleotides by the Guanidinium Unit at the Surface of Aqueous Micelles and Bilayers. A Comparison of Microscopic and Macroscopic Interfaces

Abstract

Molecular recognition of the guanidinium/phosphate pair was investigated at microscopic interfaces of aqueous micelles and bilayers. Monoalkyl and dialkyl amphiphiles with guanidinium head groups were synthesized and dispersed in water to form micelles and bilayers having guanidinium groups at the aggregate surface. Binding of nucleotides such as AMP to these functionalized aggregates was evaluated by using an equilibrium dialysis (ultrafiltration) method. The observed binding constants of 102−104 M-1 are much larger than the corresponding binding constant reported for a monomerically dispersed pair in the aqueous phase (1.4 M-1) but are smaller than those found at the macroscopic air−water interface (106−107 M-1). Therefore, the macroscopic interface promotes guanidinium−phosphate interaction more effectively than the microscopic interface. The present finding indicates that the microscopic interface can strengthen hydrogen bonding and/or electrostatic interaction even in the presence of water. Saturation binding phenomena were different between micelles and bilayers. All of the guanidinium groups in fluid micelles are effective for phosphate binding, but part of the guanidinium group in bilayers are not effective probably because of steric restriction.

The design of guanidinium-rich transporters and their internalization mechanisms

“…Structure-function relationships of fluorescently labeled peptides inspired by Tat [49][50][51][52][53][54][55][56][57] In 1996, we started a program directed at designing molecular transporters that would be superior to the Tat 9-mer (RKKRRQRRR or Tat [49][50][51][52][53][54][55][56][57] ) in performance and in cost, thereby allowing for broader exploitation of transporter-based drug delivery for therapeutic applications. Our selection of the Tat 9-mer as a starting point relative to other transporter leads was influenced by the rather paradoxical but potentially therapeutically valuable behavior of this lead: it is highly polar and thus readily soluble in water -a factor that could be exploited in therapeutic administration -but unlike most polar systems it readily passes through the nonpolar membrane of cells.…”

“…These proved to be very effective transporters. For example, the carbamate 9-mer 6 (n=9) translocates into cells 2.3 times faster than the D-arg 9-mer (4, n=9) which itself is taken up into cells approximately three times faster than Tat [49][50][51][52][53][54][55][56][57] . While many studies address only cellular uptake, this study also showed that the oligocarbamate transporters penetrate mouse skin, a finding of much significance as the skin represents a much more formidable barrier than the plasma membrane and is the key barrier for many dermatological applications.…”

Application of Gold Nanoparticles to Spectrophotometric Sensing of Hydrophilic Anions Based on Molecular Recognition by Urea Derivative

“…Kunitake's group reported on the enhanced binding-ability of guanidiniummonolayers at an air-water interface. 15,16 Anion recognition by a thiourea-based chromoionophore loaded in a cationic vesicle has also been reported. 17 Isothiouronium-derived LangmuirBlodgett (LB) film at an air-water interface has been investigated to detect the interfacial binding of H2PO4 -in aqueous subphase by UV-vis spectroscopy.…”

New families of mesoporous materials

“…Immobilization of biomaterials into nanoorganized structures, including supermolecules [108][109][110][111][112][113], lipid bilayers [114][115][116][117][118][119][120][121][122][123][124][125][126], self-assembled monolayers [127][128][129], Langmuir-Blodgett films [130][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145][146][147][148][149], and layerby-layer assemblies [150][151][152][153][154][155][156]…”