Mice that are deficient in either the Pms2 or Msh2 DNA mismatch repair genes have microsatellite instability and a predisposition to tumours. Interestingly, Pms2-deficient males display sterility associated with abnormal chromosome pairing in meiosis. Here mice deficient in another mismatch repair gene, Mlh1, possess not only microsatellite instability but are also infertile (both males and females). Mlh1-deficient spermatocytes exhibit high levels of prematurely separated chromosomes and arrest in first division meiosis. We also show that Mlh1 appears to localize to sites of crossing over on meiotic chromosomes. Together these findings suggest that Mlh1 is involved in DNA mismatch repair and meiotic crossing over.

Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.

A. Sample preparationThe YBa 2 Cu 3 O 6.5 (YBCO) single crystal used here was grown by top-seeded solution growth using a Ba 3 Cu 5 O solvent [1]. The as-grown single crystal was first annealed at 700°C for 70 h with flowing oxygen and quenched down to room temperature. The La 1.85 Sr 0.15 CuO 4 (LSCO) single crystal was synthesised by a travelling-solvent-floating-zone method utilizing infrared radiation furnaces (Crystal system, FZ-T-4000) and annealed in oxygen gas under ambient pressure at 600°C for 7 days[2]. B. Femtosecond pump-probe set-upA detailed description of the set-up used is found in [3]. In a "pump-probe" experiment, a "pump" pulse excites the sample and the induced change in transmission or reflection of a delayed probe pulse monitors the relaxation behaviour. In the linear approximation ∆R R directly tracks the electronic relaxation processes, and the time constants obtained from fits of its dynamics are the characteristic times of the underlying relaxation processes. In our data, this approximation is justified by two essential characteristics: (i) the ∆R R amplitude is linear in the excitation intensity (see Figure 1a for LSCO), and (ii) the same decay times appear independently of the probe wavelength, only with different spectral weights of the individual components.In order to resolve the dynamics of fast processes very short pulses are necessary, since the instrumental response function is given by the cross correlation between the pump and probe pulses. We use sub-10 fs probe pulses from an ultrabroadband (covering a spectral range from 500 to 700 nm) non-collinear optical parametric amplifier (NOPA) and ∼15 fs pump pulses from a narrower band (wavelength tunable, in our case centred at 530 nm) NOPA. The seed pulses for the NOPAs and the amplified pulses are steered and focussed exclusively with reflecting optics to avoid pulse chirping.A schematic of the experimental apparatus is shown in Fig. 1. The laser source is a regeneratively amplified modelocked Ti:sapphire laser (Clark-MXR Model CPA-1), delivering pulses at 1 kHz repetition rate with 780 nm center wavelength, 150 fs duration, and 500 µJ energy. Both NOPAs are pumped by the second harmonic of the Ti:sapphire laser, which is generated in a 1-mm-thick lithium triborate crystal (LBO), cut for type-I phase matching in the XY plane (θ = 90°, ϕ = 31.68°, Shandong Newphotons).The ultrabroadband visible NOPA that generates the probe pulses has been described in detail before[4]; a schematic of it is shown in Fig. 2. The white light continuum seed pulses are generated by a small fraction of the fundamental

Because of the rapid rise of the efficiency, perovskite solar cells are currently considered as the most promising next-generation photovoltaic technology. Much effort has been made to improve the efficiency and stability of perovskite solar cells. Here, it is demonstrated that the addition of a novel organic cation of 2-(6-bromo-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)ethan-1-ammonium iodide (2-NAM), which has strong Lewis acid and base interaction (between CO and Pb) with perovskite, can effectively increase crystalline grain size and reduce charge carrier recombination of the double cation FA MA PbI Br perovskite film, thus boosting the efficiency from 17.1 ± 0.8% to 18.6 ± 0.9% for the 0.1 cm cell and from 15.5 ± 0.5% to 16.5 ± 0.6% for the 1.0 cm cell. The champion cell shows efficiencies of 20.0% and 17.6% with active areas of 0.1 and 1.0 cm , respectively. Moreover, the hysteresis behavior is suppressed and the stability is improved. The result provides a promising route to further elevate efficiency and stability of perovskite solar cells by the fine tuning of triple organic cations.

Figure 5. Photographs of a) letters written using aqueous poly-BrNpA solution before and after drying, upon light irradiation at 365 nm; and b) a number '8' written using aqueous poly-BrBA (outer frame) and poly-BrNp (cross-bar) solution, taken under different light irradiation. 1401 wileyonlinelibrary.com

A bead model to determine the electrophoretic mobilities and translational diffusion constants of weakly charged peptides is developed that is based on a approximate structural model of peptides and is also grounded in electrohydrodynamic theory. A peptide made up of X amino acids is modeled as N=2X beads with 2 beads representing each amino acid in the chain. For the two beads representing a particular amino acid in a peptide, the radius of one bead is set to one-half the nearest neighbor Calpha-Calpha distance, and the radius of the other bead is chosen on the basis of the diffusion constant of the free amino acid. Peptide conformations, which are defined by a set of psi-phi dihedral angles, are randomly generated by using the transformation matrix approach of Flory (Flory, P. Statistical Mechanics of Chain Molecules; John Wiley: New York, 1969) and rejecting conformations which result in bead overlap. The mobility and diffusion constants are computed for each conformation and at least 100 independent conformations are examined for each peptide. In general, the mobility is found to depend only weakly on peptide conformation. Model and experimental mobilities are compared by examining the data of Janini and co-workers (Janini, G.; et al. J. Chromatogr. 1999, 848, 417-433). A total of 58 peptides consisting of from 2 to 39 amino acids are considered. The average relative error between experimental and model mobilities is found to be 1.0% and the rms relative error 7.7%. In specific cases, the discrepancy can be substantial and possible reasons for this are discussed. It should be emphasized that the input parameters of the peptide model are totally independent of experimental mobilities. It is hoped that the peptide model developed here will be useful in the prediction of peptide mobility as well as in using peptide mobilities to extract information about peptide structure, conformation, and charge. Finally, we show how simultaneous measurements of translational diffusion and mobility can be used to estimate peptide charge.

We measure magnetic quantum oscillations in the underdoped cuprates YBa2Cu3O6+x with x = 0.61, 0.69, using fields of up to 85 T. The quantum-oscillation frequencies and effective masses obtained suggest that the Fermi energy in the cuprates has a maximum at p ≈ 0.11 − 0.12. On either side, the effective mass may diverge, possibly due to phase transitions associated with the T = 0 limit of the metal-insulator crossover (low-p side), and the postulated topological transition from small to large Fermi surface close to optimal doping (high p side).

We measure the anisotropic midinfrared response of electrons and phonons in bulk YBa(2)Cu(3)O(7-δ) after femtosecond photoexcitation. A line shape analysis of specific lattice modes reveals their transient occupation and coupling to the superconducting condensate. The apex oxygen vibration is strongly excited within 150 fs, demonstrating that the lattice absorbs a major portion of the pump energy before the quasiparticles are thermalized. Our results attest to substantial electron-phonon scattering and introduce a powerful concept probing electron-lattice interactions in a variety of complex materials.