Biomimetic membranes with aqueous nano channels but without proteins: impedance of impregnated cellulose ester filters

Earlier we have shown that many important properties of ionic aqueous channels in biological membranes can be imitated using simple biomimetic membranes. These membranes are composed of mixed cellulose ester-based filters, impregnated with isopropyl myristate or other esters of fatty acids, and can be used for high-throughput drug screening. If the membrane separates two aqueous solutions, combination of relatively hydrophilic polymer support with immobilized carboxylic groups results in the formation of thin aqueous layers covering inner surface of the pores, while the pore volume is filled by lipid-like substances. Because of these aqueous layers biomimetic membranes even without proteins have a cation/anion ion selectivity and specific (per unit of thickness) electrical properties, which are similar to typical properties of biological membranes. Here we describe frequency-dependent impedance of the isopropyl myristate-impregnated biomimetic membranes in the 4-electrode arrangement and present the results as Bode and Nyquist diagrams. When the membranes are placed in deionized water, it is possible to observe three different dispersion processes in the frequency range 0.1 Hz to 30 kHz. Only one dispersion is observed in 5 mM KH(2)PO(4) solution. It is suggested that these three dispersion features are determined by (a) conductivity in aqueous structures/channels, formed near the internal walls of the filter pores at high frequencies, (b) dielectric properties of the whole membrane at medium frequencies, determined by polymer support, aqueous layers and impregnating oil, and, finally, (c) by the processes in hydrated liquid crystal structures formed in pores by impregnating oil in contact with water at low frequencies.     

Exciplex Formation and Excited State Deactivation of Difluoroborondipyrromethene (Bodipy) Dyads

Two series of geometrically‐related dyads are discussed based on the difluoroborondipyrromethene (Bodipy) unit, and incorporating covalently attached hydroquinone/quinone groups. These units are anchored directly, or via a phenylene spacer, to the Bodipy core at the meso position in one series ( BD‐MHQ , BD‐MQ , BD‐MPHQ , BD‐MPQ ), but for the second series the attachment site is the 2‐position ( BD‐SHQ , BD‐SQ , BD‐SPHQ , BD‐SPQ ). The compounds show various levels of fluorescence depending on the oxidation state of the appended group and the substitution pattern. In non‐polar solvents such as toluene, diethyl ether and dichlorobenzene, the S₁ state deactivation of the Bodipy unit in BD‐SPQ and BD‐MPQ is dominated by ^{1, 3}exciplex formation, which has not been reported for Bodipy derivatives so far. In the latter molecule, the decay of the exciplex is divided between population of the Bodipy triplet state (13 %–21 %) and ground state reformation. This partitioning is not seen for the side‐on substituted derivative, BD‐SPQ , and only ground state reformation is observed following decay of the exciplex. This difference in behavior is explained by the radical‐pair inter‐system‐crossing mechanism, which more effectively operates in BD‐MPQ because of the orthogonality of the donor‐acceptor units. In the more polar solvent CH₃CN all the quinone derivatives show fast formation of the charge‐separated state (k_CS) followed by slower charge recombination (k_CR). The ratio k_CS/k_CR≤80.     

Profiling and characterisation by liquid chromatography/multi-stage mass spectrometry of the chlorogenic acids in Gardeniae Fructus

The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source.     

Improved measurement of the hydrogen 1S-2S transition frequency

We have measured the 1S-2S transition frequency in atomic hydrogen via two-photon spectroscopy on a 5.8 K atomic beam. We obtain f(1S-2S) = 2,466,061,413,187,035 (10) Hz for the hyperfine centroid, in agreement with, but 3.3 times better than the previous result [M. Fischer et al., Phys. Rev. Lett. 92, 230802 (2004)]. The improvement to a fractional frequency uncertainty of 4.2 × 10(-15) arises mainly from an improved stability of the spectroscopy laser, and a better determination of the main systematic uncertainties, namely, the second order Doppler and ac and dc Stark shifts. The probe laser frequency was phase coherently linked to the mobile cesium fountain clock FOM via a frequency comb.     

Towards Higgs boson production in gluon fusion to NNLO in the MSSM

We consider the Higgs boson production in the gluon-fusion channel to next-to-next-to-leading order within the Minimal Supersymmetric Standard Model. In particular, we present analytical results for the matching coefficient of the effective theory and study its influence on the total production cross section in the limit where the masses of all MSSM particles coincide. For supersymmetric masses below 500 GeV it is possible to find parameters leading to a significant enhancement of the Standard Model cross section, the K-factors, however, change only marginally.     

Exact solutions of the generalized Bretherton equation

The generalized Bretherton equation is studied. The Bäcklund transformations between traveling wave solutions of the generalized Bretherton equation and solutions of polynomial ordinary differential equation are constructed. The classification problem for meromorphic solutions of the latter equation is discussed. Several new families of exact solutions for the generalized Brethenton equation are given.     

Estimates of invariant distances on “convex” domains

Estimates for invariant distances of convexifiable, \(\mathbb{C }\) -convexifiable and planar domains are given.     

Theoretical analysis of an optimal control problem of conductive–convective–radiative heat transfer

The problem of optimal heat removal from a three-dimensional domain is considered. The specific of the study consist in accounting for the radiative heat transfer. The so-called P₁ approximation of the radiative heat transfer equation is used, which reduces the model to a nonlinear elliptic system. A problem of optimal boundary control of this system is considered. The solvability of the control problem is proved, and necessary optimality conditions of first order are derived. Examples of non-singularity of these conditions are given.     

Big elements in irreducible linear groups

Let V be a linear space over a field K of dimension n > 1, and let \({G \leq {\rm GL}(V)}\) be an irreducible linear group. In this paper we prove that the group G contains an element g such that rank \({(g - \alpha E_{n}) \geq \frac{n}{2}}\) for every \({\alpha \in K}\) , where E _n is the identity operator on V. This estimate is sharp for any \({n = 2^{m}}\) . The existence of such an element implies that the conjugacy class of G in GL(V) intersects the big Bruhat cell \({B\dot{w}_{0}B}\) of GL(V) non-trivially (here B is a fixed Borel subgroup of G). The latter fact is equivalent to the existence of a complete flag \({\mathfrak{F}}\) such that the flags \({g(\mathfrak{F}), \mathfrak{F}}\) are in general position for some g ∈ G.