modulation factor
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2021 ◽  
Vol 10 (1) ◽  
pp. 33
Author(s):  
Yasushi Maki ◽  
Hideji Yoshida

Bacteria convert active 70S ribosomes to inactive 100S ribosomes to survive under various stress conditions. This state, in which the ribosome loses its translational activity, is known as ribosomal hibernation. In gammaproteobacteria such as Escherichia coli, ribosome modulation factor and hibernation-promoting factor are involved in forming 100S ribosomes. The expression of ribosome modulation factor is regulated by (p)ppGpp (which is induced by amino acid starvation), cAMP-CRP (which is stimulated by reduced metabolic energy), and transcription factors involved in biofilm formation. This indicates that the formation of 100S ribosomes is an important strategy for bacterial survival under various stress conditions. In recent years, the structures of 100S ribosomes from various bacteria have been reported, enhancing our understanding of the 100S ribosome. Here, we present previous findings on the 100S ribosome and related proteins and describe the stress-response pathways involved in ribosomal hibernation.


2021 ◽  
Vol 8 ◽  
Author(s):  
Hideji Yoshida ◽  
Hideki Nakayama ◽  
Yasushi Maki ◽  
Masami Ueta ◽  
Chieko Wada ◽  
...  

One of the important cellular events in all organisms is protein synthesis, which is catalyzed by ribosomes. The ribosomal activity is dependent on the environmental situation of the cell. Bacteria form 100S ribosomes, lacking translational activity, to survive under stress conditions such as nutrient starvation. The 100S ribosome is a dimer of two 70S ribosomes bridged through the 30S subunits. In some pathogens of gammaproteobacteria, such as Escherichia coli, Yersinia pestis, and Vibrio cholerae, the key factor for ribosomal dimerization is the small protein, ribosome modulation factor (RMF). When ribosomal dimerization by RMF is impaired, long-term bacterial survival is abolished. This shows that the interconversion system between active 70S ribosomes and inactive 100S ribosomes is an important survival strategy for bacteria. According to the results of several structural analyses, RMF does not directly connect two ribosomes, but binds to them and changes the conformation of their 30S subunits, thus promoting ribosomal dimerization. In this study, conserved RMF amino acids among 50 bacteria were selectively altered by mutagenesis to identify the residues involved in ribosome binding and dimerization. The activities of mutant RMF for ribosome binding and ribosome dimerization were measured using the sucrose density gradient centrifugation (SDGC) and western blotting methods. As a result, some essential amino acids of RMF for the ribosomal binding and dimerization were elucidated. Since the induction of RMF expression inhibits bacterial growth, the data on this protein could serve as information for the development of antibiotic or bacteriostatic agents.


2021 ◽  
Vol 20 ◽  
pp. 153303382110454
Author(s):  
Akihiko Ishibashi ◽  
Hiromasa Kurosaki ◽  
Kosei Miura ◽  
Nobuko Utsumi ◽  
Hideyuki Sakurai

Objectives: Hippocampus-sparing whole-brain radiotherapy (HS-WBRT) using tomotherapy is known to provide a better dose distribution than volumetric-modulated arc therapy but requires an extended irradiation time. The present study aimed to investigate whether irradiation time can be shortened by reducing the modulation factor (MF) without losing the target dose distribution. Methods: Using six tilted computed tomography images in the head area, the planning target volume (PTV) and hippocampal doses, and the irradiation time was investigated with a jaw width of 1 cm, a pitch of 0.200, and the MF changed from 3.0 to 2.6, 2.2, 1.8, and 1.4. Results: No significant changes in the PTV or hippocampus were found with MF in the range from 3.0 to 1.8, but marked deterioration was found with that of 1.4. The irradiation time showed a linear relationship with the MF within the range from 3.0 to 1.8, with 1334, 1158, 986, and 817 s at modulation factors of 3.0, 2.6, 2.2, and 1.8, respectively. However, when the MF was 1.4, the irradiation time was 808 s. Conclusions: When HS-WBRT is performed with a tilted body position and a jaw width of 1 cm, with a MF of 1.8, a favorable balance between dose parameters and irradiation time is achieved, whereas with a MF of 1.4, the quality of the radiotherapy plan deteriorates, and the irradiation time is approximately the same as that with a MF of 1.8.


2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
K. Ganapathy ◽  
...  

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% (D98%) and 2% (D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ± 1.80% of planned and IC measurement. The planned dose distribution agreed with reconstructed and ArcCheck measured dose with mean (SD) 3Dγ of 98.70% (1.57%) and 2Dγ of 99.48% (0.81%). The deviation in D98% and D2% were within 1.71% and 4.10% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agreed within ± 1.20%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from the five upper body TMI/TMLI plans showed mean ± SD 2Dγ of 97.82% ± 1.27%, the reconstruction method resulted poor mean (SD) 3Dγ of 92.00% (± 5.83%), 64.80% (± 28.28%), 69.20% (± 30.46%), 60.80% (± 19.37%) and 73.2% (± 20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were < 3.80% and 9.50%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% < 1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5 cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.


2020 ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
Ganapathy Krishnan ◽  
...  

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for total marrow (TMI) and Lymphoid (TMLI) irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured leaf open time sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98%(D98%) and 2%(D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ±1.8% of planned and IC measurement. The planned dose distribution agrees with reconstructed and ArcCheck measured dose with mean(SD) 3Dγ of 98.7%(1.57%) and 2Dγ of 99.48%(0.81%). The deviation in D98% and D2% were within 1.71% and 4.1% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agrees within ±1.2%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from five upper body TMI/TMLI plans showed mean±SD 2Dγ of 97.82%±1.27%, the reconstruction method resulted poor mean(SD) 3Dγ of 92.00%(±5.83%), 64.80%(±28.28%), 69.20%(±30.46%), 60.80%(±19.37%) and 73.2% (±20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were <3.8% and 9.5%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% <1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.


2020 ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
Ganapathy Krishnan ◽  
...  

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for total marrow (TMI) and Lymphoid (TMLI) irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured leaf open time sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98%(D98%) and 2%(D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ±1.8% of planned and IC measurement. The planned dose distribution agrees with reconstructed and ArcCheck measured dose with mean(SD) 3Dγ of 98.7%(1.57%) and 2Dγ of 99.48%(0.81%). The deviation in D98% and D2% were within 1.71% and 4.1% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agrees within ±1.2%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from five upper body TMI/TMLI plans showed mean±SD 2Dγ of 97.82%±1.27%, the reconstruction method resulted poor mean(SD) 3Dγ of 92.00%(±5.83%), 64.80%(±28.28%), 69.20%(±30.46%), 60.80%(±19.37%) and 73.2% (±20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were <3.8% and 9.5%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% <1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.


2020 ◽  
Vol 10 (7) ◽  
pp. 2427
Author(s):  
Rongbin She ◽  
Wenquan Liu ◽  
Guanglu Wei ◽  
Yuanfu Lu ◽  
Guangyuan Li

We demonstrate terahertz single-pixel imaging is improved by using a photomodulator based on silicon passivated with SiO 2 . By exploring various SiO 2 thicknesses, we show that the modulation factor of the as-fabricated terahertz photomodulator can reach 0.9, three times that based on bare silicon. This improvement originates from chemical passivation, as well as anti-reflection. Single-pixel imaging experiments based on the compressed sensing method show that reconstructed images adopting the new photomodulator have better quality than the conventional terahertz modulator based on bare silicon. Since the passivation process is routine and low cost, we expect this work will reduce the cost of terahertz photomodulator and single-pixel THz imaging, and advance their applications.


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