The effective interaction between two like-charged macroions immersed in an electrolyte solution was studied using a Ornstein-Zernike equation with hypernetted-chain closure (HNC-OZ theory) with a particle model for the ions and solvent molecules to discuss some biological phenomena. We examined conditions under which the Coulomb interaction was greater than the thermal energy. Although the macroions repelled each other in a dilute electrolyte solution, a strong effective attraction between macroions occurred only in a medium concentration electrolyte. The effective interaction is analyzed using the superposition approximation to discuss the bond formation. When the effective attraction appears, the dense cloud of countercharged ion exists between the macroions and the cloud mediates the attraction like a covalent bond.The effective interaction between like-charged macroions is important in biological contexts, 1-9) such as in the assembly of G-actins. Another example is the coil-globule transition of DNA. 2-7) DNA is a long, negatively charged chain molecule that contains genetic information. The coilglobule transition is important in regulating the reading of information. 10) The DNA chain is stretched because of the screening repulsive interaction between parts of the chain in a dilute electrolyte solution. However, the effective interaction between these parts changes from a repulsive to an attractive interaction if multivalent cations are added to the system, and this attraction collapses the chain. This attraction mysteriously disappears when more multivalent cations are added. 6,7) As the reading of genetic information can be difficult in the globule state, the effect of reentrant behavior on the attractive interaction is important in a biological context because of differences in the accessibility of information. Similar reentrant behaviors are observed on the protein condensation. 8,9) Various theoretical studies on the attractive interactions caused by countercharged ions have been reported. Initially, the phenomenological idea of an interionic correlation was provided by Oosawa, and many other researchers have also proposed phenomenological ideas. [11][12][13] In addition to an attraction, Nguyen et al. predicted a reentrant condensation of DNA. 14) Many researchers have also explored statistical mechanics approaches using a molecular picture. [15][16][17][18][19][20][21][22][23] In 1980, Patey showed that an attractive interaction occurred between large like-charged macroions based on a study using HNC-OZ theory. 15) However, the HNC approximation remained to be clarified because of the difficulty of achieving an adequate simulation. Hence, the result of simulations provided by Valleau et al. 18) were compared with those given by the inhomogeneous HNC equation. 16,17) The good agreement between these results indicates that HNC theory gives adequate results, at least qualitatively, even if the size ratio between the small ions and the macroions is greater than 50. Following these, some new approaches ...

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-t-ButylIn order to synthesize different types of locked chromophores, it was necessary to prepare various pyrrole and pyrrolinone derivatives bearing a wide variety of functional groups. Herein we describe an oxidation of t-butyl pyrrole-2-carboxylates with o-chloranil and its application toward the synthesis of various types of functionalized pyrrolinone derivatives.

Mild hydrolysis of vinyl ether derived from a pyrrole carboxaldehyde corresponding to the B,C-ring component of phytochromobilin chromophore was achieved by treatment with oxalyl chloride in chloroform in the presence of water and ethanol to afford a one-carbon homologated aldehyde. This aldehyde was applied to the synthesis of the sterically locked 15E-anti CD-ring component of the chromophore. Furthermore, the aldehyde could be converted to the intermediate for the sterically locked 5Z-anti AB-ring component.Phytochromes are chromoproteins that have a linear tetrapyrrole chromophore, which is covalently bound to the protein and responds to red and far-red light through a reversible interchange between the red light-absorbing (Pr) and the far-red-light-absorbing (Pfr) forms. Land plants use phytochromobilin (PΦB),