Optical activities of helical polymers: a crystal orbital theory based on Wannier functions

2021 ◽  
Vol 140 (11) ◽  
Author(s):  
M. Hatanaka
2011 ◽  
Vol 964 (1-3) ◽  
pp. 269-276
Author(s):  
Luis Rincón ◽  
Omar Quintanilla ◽  
Lissette Alarcon ◽  
Rafael Almeida

Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.


2020 ◽  
Author(s):  
Gabriel Freire Sanzovo Fernandes ◽  
Leonardo dos Anjos Cunha ◽  
Francisco Bolivar Correto Machado ◽  
Luiz Ferrão

<p>Chemical bond plays a central role in the description of the physicochemical properties of molecules and solids and it is essential to several fields in science and engineering, governing the material’s mechanical, electrical, catalytic and optoelectronic properties, among others. Due to this indisputable importance, a proper description of chemical bond is needed, commonly obtained through solving the Schrödinger equation of the system with either molecular orbital theory (molecules) or band theory (solids). However, connecting these seemingly different concepts is not a straightforward task for students and there is a gap in the available textbooks concerning this subject. This work presents a chemical content to be added in the physical chemistry undergraduate courses, in which the framework of molecular orbitals was used to qualitatively explain the standard state of the chemical elements and some properties of the resulting material, such as gas or crystalline solids. Here in Part 1, we were able to show the transition from Van der Waals clusters to metal in alkali and alkaline earth systems. In Part 2 and 3 of this three-part work, the present framework is applied to main group elements and transition metals. The original content discussed here can be adapted and incorporated in undergraduate and graduate physical chemistry and/or materials science textbooks and also serves as a conceptual guide to subsequent disciplines such as quantum chemistry, quantum mechanics and solid-state physics.</p>


1989 ◽  
Author(s):  
Alfred B. Anderson ◽  
Paul Shiller ◽  
Eugene A. Zarate ◽  
Claire A. Tessier-Youngs ◽  
Wiley J. Youngs

Author(s):  
Wai-Kee Li ◽  
Hung Kay Lee ◽  
Dennis Kee Pui Ng ◽  
Yu-San Cheung ◽  
Kendrew Kin Wah Mak ◽  
...  

The First Edition of this book, which appeared in 2013, serves as a problem text for Part I (Fundamentals of Chemical Bonding) and Part II (Symmetry in Chemistry) of the book Advanced Structural Inorganic Chemistry published by Oxford University Press in 2008. A Chinese edition was published by Peking University Press in August in the same year. Since then the authors have received much feedback from users and reviewers, which prompted them to prepare a Second Edition for students ranging from freshmen to senior undergraduates who aspire to attend graduate school after finishing their first degree in Chemistry. Four new chapters are added to this expanded Second Edition, which now contains over 400 problems and their solutions. The topics covered in 13 chapters follow the sequence: electronic states and configurations of atoms and molecules, introductory quantum chemistry, atomic orbitals, hybrid orbitals, molecular symmetry, molecular geometry and bonding, crystal field theory, molecular orbital theory, vibrational spectroscopy, crystal structure, transition metal chemistry, metal clusters: bonding and reactivity, and bioinorganic chemistry. The problems collected in this volume originate from examination papers and take-home assignments that have been part of the teaching program conducted by senior authors at The Chinese University of Hong Kong over nearly a half-century. Whenever appropriate, source references in the chemical literature are given for readers who wish to delve deeper into the subject. Eight Appendices and a Bibliography listing 157 reference books are provided to students and teachers who wish to look up comprehensive presentations of specific topics.


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