Structural modification of bovine milk β-lactoglobulin (β-LG) in aqueous 1-butyl-3-methylimidazolium nitrate ([bmim][NO3]) and ethylammonium nitrate ([EAN][NO3]) solutions has been investigated by Fourier transform infrared and circular dichroism spectroscopy. Remarkably, high ionic liquid (IL) concentrations (>15 mol %IL) caused formation of a non-native α-helical structure of β-LG and disruption of its tertiary structure. Furthermore, while [bmim][NO3] promoted protein aggregation, [EAN][NO3] inhibited it probably owing to differences in the unique solution structure (nanoheterogeneity) of the ILs by the different cationic species. The IL-induced α-helical formation of β-LG shows a behavior similar to the alcohol denaturation, but a disordered structure-rich state was observed in the β-α transition process by adding IL, in contrast to the case of an aqueous alcohol solution of protein. We propose that the molten salt-like property of aqueous IL solutions strongly support α-helical formation of proteins.

We have obtained a new high-resolution K ′ -band image of the central region of the rich X-ray cluster RX J0848.9+4452 at z=1.26. We found that the brightest cluster galaxy (BCG) in the cluster is clearly separated into two distinct objects. Whereas the optical to near-infrared colors of the objects are consistent with the predictions of passive evolution models for galaxies formed at high redshift, the luminosities of the two galaxies are both considerably fainter than predicted by passive evolution of BCG's in low and intermediate redshift clusters. We argue that this is evidence of an on-going merger of normal cluster ellipticals to form the dominant galaxy in the core of RX J0848.9+4452. The two galaxies appear to point towards the nearby cluster ClG J0848+4453 Stanford et al. (1997) and are aligned with the outer X-ray contour of their parent cluster, supporting a model of BCG formation by collimated infall along the surrounding large-scale structure.

The conformational stability of 1-alkyl-3-methylimidazolium tetrafluoroborate ([Cmim][BF], n = 3-8) under high pressure was investigated using Raman spectroscopy to reveal the preferential role of the alkyl-chain length (n) in high-pressure glass transition. To evaluate this, we determined the intensity ratio (r) and differences in the partial molar volume (ΔV) between the whole trans and gauche conformers of the [Cmim] cation using Raman intensities. Interestingly, both values were classified into a two alkyl-chain length region at the border of n = 5. The coulombic interaction (cation-anion interaction) for the conformational stability is the predominant factor below n = 5 (the cation-head portion: alkyl carbon number C < 5), and the alkyl-chain packing effect (cation-cation interaction) is the predominant factor above n = 5 (the cation-tail portion: C > 5). In combination with the conformational preference of the [Cmim] cation under a high-pressure glassy state, the alkyl chain displays a preferential role, i.e., an increase in the gauche conformer of [Cmim][BF] adjusts to avoid crystallization (the conformational adjustment effect). In the presence of the coulombic interaction, the preferential role of the flexible alkyl chain is an important key to elucidate the mechanism of the complicated high-pressure phase transition behavior of ionic liquids.

We investigated the stability of the liquid phase of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Cmim][TFSI]) homologues with different alkyl chain lengths for 3 ≤ n ≤ 10 at room temperature. We found that all [Cmim][TFSI] samples (n = 3-10) formed a glassy state when pressure was applied. Intriguingly, the glass transition pressure (p) slightly increases up to n = 5, reaches a plateau at n ≧ 8, and increases again at n = 10. This is completely different from the high-pressure glass formation of [Cmim][BF], where the p decreases as n increases. We discussed the local structural changes occurring in [Cmim][TFSI] in view of the conformational changes of the cation and anion, and small-angle X-ray scattering data. It seems that [Cmim][TFSI] is resistant to external pressure and retains its local liquid structure by conformational adjustments of the cation and anion.