A Chemical Biology Approach to Understanding Molecular Recognition of Lipid II by Nisin(1–12): Synthesis and NMR Ensemble Analysis of Nisin(1–12) and Analogues

Natural products that target lipid II, such as the lantibiotic nisin, are strategically important in the development of new antibacterial agents to combat the rise of antimicrobial resistance. Understanding the structural factors that govern the highly selective molecular recognition of lipid II by the N-terminal region of nisin, nisin(1–12), is a crucial step in exploiting the potential of such compounds. In order to elucidate the relationships between amino acid sequence and conformation of this bicyclic peptide fragment, we have used solid-phase peptide synthesis to prepare two novel analogues of nisin(1–12) in which the dehydro residues have been replaced. We have carried out an NMR ensemble analysis of one of these analogues and of the wild-type nisin(1–12) peptide in order to compare the conformations of these two bicyclic peptides. Our analysis has shown the effects of residue mutation on ring conformation. We have also demonstrated that the individual rings of nisin(1–12) are pre-organised to an extent for binding to the pyrophosphate group of lipid II, with a high degree of flexibility exhibited in the central amide bond joining the two rings.     

Rain,power laws,and advection

Localized rain events have been found to follow power-law size and duration distributions over several decades, suggesting parallels between precipitation and seismic activity [O. Peters, Phys. Rev. Lett. 88, 018701 (2002)]]. Similar power laws are generated by treating rain as a passive tracer undergoing advection in a velocity field generated by a two-dimensional system of point vortices.     

Cadmium copper tetrachloride tetrahydrate

The double salt [CuCl₂(H₂O)₂{CdCl₂}]·2H₂O crystallizes in the triclinic rather than the monoclinic system as reported previously. The structure consists of sheets in the ac plane with slightly distorted octahedral CdCl₆ [Cd—Cl 2.5813 (8)–2.6943 (8) Å] connected by Cd—Cl—Cd bridges in the Cd equatorial plane along a , and by Cd—Cl—Cu bridges to layers of square‐planar CuCl₂(H₂O)₂ along c . There are long axial Cu—Cl interactions of 2.8623 (7) Å and additional water of hydration is hydrogen bonded to coordinated water and chloride ligands. The additional water connects the ac sheets into a three‐dimensional network. Both Cd and Cu occupy different sites. The Cu?Cu and Cd?Cd distances are 3.8274 (6) Å.     

New lanthanide-containing polytungstates derived from the cyclic P8W48 Anion: {Ln4(H2O)28[K subset P8W48O184(H4W4O12)2Ln2(H2O)10]13-}x, Ln = La, Ce, Pr, Nd

The reaction of K28Li5H7[P8W48O184].92H2O with early lanthanides under hydrothermal and conventional conditions yields novel structures of the molecular formula Ln4(H2O)28K6Li7[K subsetP8W48O184(H4W4O12)2Ln2(H2O)10] congruent with 57H2O, Ln = La (1), Ce (2, 2a), Pr (3), Nd (4), in which the central cavity of the precursor anion is occupied by lanthanide cations and H4W4O12 moieties. The new heteropolyanions were characterized by elemental analysis, infrared spectroscopy, 31P NMR, and X-ray crystallography. All of the crystals are monoclinic, space group C2/m, with lattice constants (A, Epsilon) a = 33.061(3), b = 30.986(3), c = 15.1649(13), beta = 103.607(2), (1); a = 33.0577(16), b = 31.0562(15), c = 15.2320(7), beta = 104.015(2), (2); a = 33.0577(16), b = 31.0562(15), c = 15.2320(7), beta = 104.015(2), (2a); a = 33.007(2), b = 31.060(2), c = 15.2129(10), beta = 104.0140(10), (3); a = 32.913(19), b = 31.155(18), c = 15.135(9), beta = 103.495(11), (4); and Z = 2.