Faculty Opinions recommendation of High-resolution 3D NMR structure of the KRAS proto-oncogene promoter reveals key features of a G-quadruplex involved in transcriptional regulation.

Introduction. X-ray inspection plays a unique role among all nondestructive testing methods for products and materials due to sufficiently high resolution and high penetrability. The present study is designed to consider the key features of microfocus X-ray sources, their areas of application, and main technical characteristics.Aim. The paper aims to systematize information and review modern X-ray radiation sources for the implementation of microfocus radiography.Materials and methods. The main designs of microfocus X-ray tubes (soldered and demountable) were considered relying on the experience of the St Petersburg State Electrotechnical University in developing and operating such equipment, as well as the experience and open-access publications of foreign researchers and developers. Data collected by leading research teams over the last ten years were analyzed.Results. The paper presents design features for each main type of microfocus X-ray tubes – soldered and demountable. All key structural elements are considered: an anode assembly, a cathode assembly, and a focusing system. The influence of anode target material on the X-ray tube radiation spectrum is shown. An original design of a liquid-anode microfocus X-ray tube is described to demonstrate its key features and advantages. In addition, the paper gives an overview of cathodes used in microfocus X-ray tubes (tungsten cathode and lanthanum hexaboride cathode), as well as providing a detailed description of calculations performed for focusing systems. Finally, the designs of modern X-ray tubes are presented.Conclusion. Modern X-ray tubes are high-tech products that allow for high-resolution research of various objects. The main advantage of testing performed with the use of X-ray tubes consists in high resolution (micron and submicron). The X-ray images of test objects used to determine their spatial resolution are given, which clearly illustrate the vast possibilities of this technology. In addition, ways to improve microfocus X-ray tubes are briefly discussed. The considered materials can be useful in selecting a nondestructive testing tool, as well as in developing and creating X-ray systems on the basis of microfocus X-ray tubes.

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Transcriptional Regulation By G-Quadruplex Sequences In Hypoxic Pulmonary Artery Endothelial Cells (PAECs)

10.1164/ajrccm-conference.2010.181.1_meetingabstracts.a3940 ◽

2010 ◽

Author(s):

David W. Clark ◽

Tzu L. Phang ◽

M. Edwards ◽

Mark W. Geraci ◽

Mark N. Gillespie

Keyword(s):

Endothelial Cells ◽

Transcriptional Regulation ◽

Pulmonary Artery ◽

G Quadruplex

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Intra-locked G-quadruplex structures formed by irregular DNA G-rich motifs

Nucleic Acids Research ◽

10.1093/nar/gkaa008 ◽

2020 ◽

Vol 48 (6) ◽

pp. 3315-3327 ◽

Cited By ~ 8

Author(s):

Arijit Maity ◽

Fernaldo Richtia Winnerdy ◽

Weili Denyse Chang ◽

Gang Chen ◽

Anh Tuân Phan

Keyword(s):

Human Genome ◽

Dna Sequences ◽

Structural Features ◽

Nmr Structure ◽

Solution Nmr ◽

Structural Studies ◽

High Propensity ◽

G Quadruplex ◽

High Prevalence

Abstract G-rich DNA sequences with tracts of three or more continuous guanines (G≥3) are known to have high propensity to adopt stable G-quadruplex (G4) structures. Bioinformatic analyses suggest high prevalence of G-rich sequences with short G-tracts (G≤2) in the human genome. However, due to limited structural studies, the folding principles of such sequences remain largely unexplored and hence poorly understood. Here, we present the solution NMR structure of a sequence named AT26 consisting of irregularly spaced G2 tracts and two isolated single guanines. The structure is a four-layered G4 featuring two bi-layered blocks, locked between themselves in an unprecedented fashion making it a stable scaffold. In addition to edgewise and propeller-type loops, AT26 also harbors two V-shaped loops: a 2-nt V-shaped loop spanning two G-tetrad layers and a 0-nt V-shaped loop spanning three G-tetrad layers, which are named as VS- and VR-loop respectively, based on their distinct structural features. The intra-lock motif can be a basis for extending the G-tetrad core and a very stable intra-locked G4 can be formed by a sequence with G-tracts of various lengths including several G2 tracts. Findings from this study will aid in understanding the folding of G4 topologies from sequences containing irregularly spaced multiple short G-tracts.

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