抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

To say that this is the best book on the quantum theory of fields is no praise, since to my knowledge it is the only book on this subject But it is a very good and most useful book The original was written in German and appeared in 1942 This is a translation with some minor changes A few remarks have been added, concerning meson theory and nuclear forces, also footnotes referring to modern work in this field, and finally an appendix on the symmetrization of the energy momentum tensor according to Belinfante Quantum Theory of Fields Prof Gregor Wentzel Translated from the German by Charlotte Houtermans and J M Jauch Pp ix + 224, (New York and London: Interscience Publishers, Inc, 1949) 36s

Quantum Theory of Fields

Combined quantum-mechanics/molecular-mechanics (QM/MM) approaches have become the method of choice for modeling reactions in biomolecular systems. Quantum-mechanical (QM) methods are required for describing chemical reactions and other electronic processes, such as charge transfer or electronic excitation. However, QM methods are restricted to systems of up to a few hundred atoms. However, the size and conformational complexity of biopolymers calls for methods capable of treating up to several 100,000 atoms and allowing for simulations over time scales of tens of nanoseconds. This is achieved by highly efficient, force-field-based molecular mechanics (MM) methods. Thus to model large biomolecules the logical approach is to combine the two techniques and to use a QM method for the chemically active region (e.g., substrates and co-factors in an enzymatic reaction) and an MM treatment for the surroundings (e.g., protein and solvent). The resulting schemes are commonly referred to as combined or hybrid QM/MM methods. They enable the modeling of reactive biomolecular systems at a reasonable computational effort while providing the necessary accuracy.

QM/MM Methods for Biomolecular Systems

(b) Write out the equations for the time dependence of ρ11, ρ22, ρ12 and ρ21 assuming that a light field interaction V = -μ12Ee iωt + c.c. couples only levels |1> and |2>, and that the excited levels exhibit spontaneous decay. (8 marks) (c) Under steady-state conditions, find the ratio of populations in states |2> and |3>. (3 marks) (d) Find the slowly varying amplitude ̃ ρ 12 of the polarization ρ12 = ̃ ρ 12e iωt . (6 marks) (e) In the limiting case that no decay is possible from intermediate level |3>, what is the ground state population ρ11(∞)? (2 marks) 2. (15 marks total) In a 2-level atom system subjected to a strong field, dressed states are created in the form |D1(n)> = sin θ |1,n> + cos θ |2,n-1> |D2(n)> = cos θ |1,n> sin θ |2,n-1>

The Quantum Theory of Light

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

We show that the second-order, two-time correlation functions for phonons and photons emitted from a vibronic molecule in a thermal bath result in bunching and anti-bunching (a purely quantum eﬀect), respectively. Signatures relating to phonon exchange with the environment are revealed in photon-photon correlations. We demonstrate that cross-correlation functions have a strong dependence on the order of detection giving insight into how phonon dynamics inﬂuences the emission of light. This work oﬀers new opportunities to investigate quantum eﬀects in condensed-phase molecular systems

Phonon signatures in photon correlations

Optical fields possess energy, momentum, and helicity. For the plane waves and paraxial fields of standard, classical optics, the spin angular momentum and optical helicity are well understood, both being proportional to the degree of circular polarization. In contrast, 3D non-paraxial optical fields generated by spatial confinement, such as tight focusing and evanescent waves, may possess spin angular momentum and optical helicity when the degree of 2D-circular polarization is zero. In this work using quantum electrodynamics we highlight two novel properties of non-paraxial optical vortices 1) a non-zero optical helicity (chirality) density for 2D-unpolarized (and 2D-linearly polarized) 3D optical vortices and 2) a longitudinal spin angular momentum density for 2D-linearly polarized 3D optical vortices.

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Optical helicity, chirality, and spin of 3D-structured Laguerre-Gaussian optical vortices

Analytical forms of the optical helicity and optical chirality of monochromatic Laguerre-Gaussian optical vortex beams are derived up to second order in the paraxial parameter $kw_0$. We show that input linearly polarised optical vortices which possess no optical chirality, helicity or spin densities can acquire them at the focal plane for values of a beam waist $w_0 \approx \lambda$ via an OAM-SAM conversion which is manifest through longitudinal (with respect to the direction of propagation) fields. We place the results into context with respect to the intrinsic and extrinsic nature of SAM and OAM, respectively; the continuity equation which relates the densities of helicity and spin; and the newly coined term Kelvins chirality which describes the extrinsic, geometrical chirality of structured laser beams. Finally we compare our work (which agrees with previous studies) to the recent article Koksal, et al. Optics Communications 490, 126907 (2021) which shows conflicting results, highlighting the importance of including all relevant terms to a given order in the paraxial parameter.

Measures of Helicity and Chirality of Optical Vortex Beams

Supramolecular structures based on Perylene Bisimides (PBIs) have been extensively studied because of their fundamental photophysical properties and for their application in a range of different optoelectronic devices. Two-dimensional electronic spectroscopy (2D-ES) is the most complete third order (χ(3)) technique, it has been shown that it is particularly useful to disentangle close-lying energy levels and to reveal dynamics in coupled molecular systems. Two different PBI covalently “head-to-tail” bound dimers (D0 and D1) with increasing interchromophoric separation, and a reference monomer (M) were synthesised and studied by means of 2D-ES in order to characterise the 1 to 2-exciton state transition and how its behaviour changes in relation to the PBI-PBI distance.

Garth A. Jones

Papers

Phonon signatures in photon correlations

Optical helicity, chirality, and spin of 3D-structured Laguerre-Gaussian optical vortices

Measures of Helicity and Chirality of Optical Vortex Beams

Excitonic coupling in covalently-bound Perylene Bisimide dimers revealed by two-dimensional electronic spectroscopy