RESUMO
The adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporter, IrtAB, plays a vital role in the replication and viability of Mycobacterium tuberculosis (Mtb), where its function is to import iron-loaded siderophores. Unusually, it adopts the canonical type IV exporter fold. Herein, we report the structure of unliganded Mtb IrtAB and its structure in complex with ATP, ADP, or ATP analogue (AMP-PNP) at resolutions ranging from 2.8 to 3.5 Å. The structure of IrtAB bound ATP-Mg2+ shows a "head-to-tail" dimer of nucleotide-binding domains (NBDs), a closed amphipathic cavity within the transmembrane domains (TMDs), and a metal ion liganded to three histidine residues of IrtA in the cavity. Cryo-electron microscopy (Cryo-EM) structures and ATP hydrolysis assays show that the NBD of IrtA has a higher affinity for nucleotides and increased ATPase activity compared with IrtB. Moreover, the metal ion located in the TM region of IrtA is critical for the stabilization of the conformation of IrtAB during the transport cycle. This study provides a structural basis to explain the ATP-driven conformational changes that occur in IrtAB.
Assuntos
Sideróforos/metabolismo , Ferro/metabolismo , Mycobacterium tuberculosis/metabolismo , Microscopia Crioeletrônica , Trifosfato de Adenosina/metabolismo , Transportadores de Cassetes de Ligação de ATPRESUMO
The corona virus disease 2019 (COVID-19), which started in Wuhan in December 2019, is a new infectious disease. The disease is highly contagious, and the correct selection of effective disinfectants is essential. This article analyzed the environmental resistance of coronavirus and its sensitivity to commonly used disinfectants by reviewing domestic and foreign literatures, and concluded that coronavirus has strong survivability in the environment, but it can be efficiently inactivated by most disinfectants. However, it should be noted that the commonly used concentration of chlorine-containing disinfectants (effective chlorine concentration of 500 mg/L) cannot quickly kill coronavirus, and a concentration of 1 000 mg/L or higher is required. Other biocidal agents, such as benzalkonium chloride and chlorhexidine digluconate, are less effective. This article aimed to provide references for selecting the appropriate disinfectants and disinfection methods to cut off the spread of the virus.
RESUMO
Objective To investigate the advantage of neuronavigation assisted microsurgical resection of gliomas in eloquent areas of brain. Methods The clinical data of 99 patients with gliomas in eloquent areas of brain and underwent microsurgery in the First Affiliated Hospital of Sun Yat-sen University from January 2012 to December 2017 were analyzed retrospectively. All patients were divided into two groups: neuronavigator-guided microsurgery group (neuronavigation group,46 cases) and non-neuronavigator-guided microsurgery group (non-neuronavigation group,53 cases). The neuronavigation group received neuronavigation assisted microsurgery, while the non-neuronavigation group received general microsurgery. MRI examination, Karnofsky performance scale (KPS) score and symptomatic improvement rate were used to analyze the extent of resection and postoperative function. Results The total resection rate of neuronavigation group was 91.3% (42/46). Comparing with 73.6% (39/53) total resection rate in non-neuronavigation group,the difference of total resection rate was statistically significant (Z=-2.343,P＜0.05). The postoperative symptoms improved both in neuronavigation group and non-neuronavigation group,and the KPS score at discharge were higher than that before operation (P＜0.05). No aggravation of symptoms and signs or new complications occurred in all patients except one case of postoperative muscle strength decline in non-neuronavigation group after the surgery. According to tumor size,the total resection rate of neuronavigation group and non-neuronavigation group among patients whose maximum size of tumor≥3cm were 89.5%(34/38) and 72.5%(37/51) respectively. The difference of total resection rate was statistically significant between these two groups (Z=-2.040,P＜0.05). Conclusion Neuronavigation assisted microsurgical resection of gliomas in brain eloquent areas can improve the rate of total resection and postoperative quality of life without increase in postoperative complications.
RESUMO
Objective To measure the dose to the primary operator and assistant operators by employing eight beam projections commonly used in coronary angiography with and without radiation protection shields in order to supply helpful guidance on radiation protection in cardiac intervention.Methods From 20 to 180 cm above the ground at the primary and assistant operators' locations,a DoseAware personal dose meter was placed in terms of an increment of 20 cm to measure radiation dose.Eight commonly used beam projections were performed,including LAO (left anterior oblique) 45°,RAO (right anterior oblique) 30°,CRAN (cranial)25°,cranial LAO (LAO45°/25°),caudal LAO(LAO45°/ 25°),CAUD (caudal) 25°,cranial RAO (RAO30°/25°),caudal RAO (caudal RAO30°/25°).Under the two different conditions,with or without radiation protection shields,the doses to the operators in the selected beam projections were respectively recorded at nine measuring positions and the shielding factor were calculated.Results The primary operator was effectively protected with radiation protection shields.In the standing area of the primary operator,except for the position at the height of 120 cm (radiation dose rate:0.35-4.78 mSv/h;shielding factor:27.67％-89.33％),the shielding factor for each measuring position was above 91％.Higher radiation doses were found at caudal LAO,LAO,and cranial LAO.The shielding factor for the assisting operator was lower than for the primary operator.In the standing area of the assisting operator (radiation dose rate:0.27-1.86 mSv/h;shielding factor:30.34％-92.13％),the peak levels were found at the height of 80,100,140 cm.And caudal RAO,caudal LAO,CRAN,LAO were found to have received higher radiation doses.Conclusions Emphasis should be attached to the use of radiation shields in coronary angiography.With radiation protection shields,higher dose is still recorded in caudal LAO,LAO,cranial LAO,caudal RAO.Furthermore,it should be paid more attention to radiation protection at 80-140 cm height,and less prolonged exposure should be employed in those beam projections mentioned above.
RESUMO
Objective To evaluate the radiation protective efficacy of different types and the positions of ceiling-suspended lead shield to the principal and assistant interventional operators in order to provide a scientific basis for the selection of optimal scheme in using ceiling-suspended lead shield. Methods At the principal and assistant interventional operators’ standing places the personal dose-measuring instruments were set up, which were placed at the height of 20 cm to 180 cm above the ground with an interval distance of 20 cm between each other. The postero-anterior (PA) projection and left lateral projection were used. The ceiling-suspended protection lead shields included lead glass (glass type) and lead glass with connected lead flexible stripe below (mixed type). The placed sites of the protection lead-shields were close to the principal operator, away from the principal operator, on the left side of the principal operator and close to the X-ray tube respectively. The radiation doses of PA projection and left lateral projection were determined. The real-time radiation dose rate and dose shielding rate at the nine measuring positions for the principal operator and assistant operator were separately calculated. The results were analyzed. Results The radiation protection of the glass type was slightly superior to that of the mixed type , but the difference was not significant. The principal operator was best protected when the shield was positioned close to him in the PA projection , and for left lateral projection the principal operator was best protected when the shield was positioned on his left side. For the assistant operator, the optimal protection was obtained when the shield was positioned close to him in both PA and left lateral projection . In the optimal position of ceiling-suspended lead shield , the highest radiation dose rate (0.71 mSv/h in glass group and 1.07 mSv/h in mixed group) was recorded on the principal operator at the height of 120 cm at PA projection, and higher radiation dose rate (≥0.47 mSv/h) was recorded on every point of both operators at the left lateral projection. Meanwhile , the overall received radiation doses of the two groups were very close. At the principal operator standing area , except for the position of 120 cm height (attenuation ratio 60.11% in glass group and 39.89% in mixed group), the attenuation ratio of each measuring point was above 93%. And the assistant operator standing area the attenuation ratio was 57%-97%. The lateral shielding ratio was generally slightly higher than PA shielding ratio. Conclusion The radiation protection effect of the two type shields is quite similar, both shields can obtain excellent protection efficacy. But the radiation dose at the height of 120 cm above the ground at PA projection is higher for the principal operator, while at lateral projection the radiation dose at all height levels is still relatively higher for both operators. Therefore, the radiation protection at the level of 120 cm height needs to be strengthened and the lateral projection exposure should be used as less as possible.
RESUMO
Objective To evaluate the radiation protective efficacy of different types and the positions of ceiling-suspended lead shield to the principal and assistant interventional operators in order to provide a scientific basis for the selection of optimal scheme in using ceiling-suspended lead shield.Methods At the principal and assistant interventional operators’ standing places the personal dose-measuring instruments were set up, which were placed at the height of 20 cm to 180 cm above the ground with an interval distance of 20 cm between each other.The postero-anterior (PA) projection and left lateral projection were used.The ceiling-suspended protection lead shields included lead glass (glass type) and lead glass with connected lead flexible stripe below (mixed type).The placed sites of the protection lead-shields were close to the principal operator, away from the principal operator, on the left side of the principal operator and close to the X-ray tube respectively.The radiation doses of PA projection and left lateral projection were determined.The real-time radiation dose rate and dose shielding rate at the nine measuring positions for the principal operator and assistant operator were separately calculated.The results were analyzed.Results The radiation protection of the glass type was slightly superior to that of the mixed type, but the difference was not significant.The principal operator was best protected when the shield was positioned close to him in the PA projection, and for left lateral projection the principal operator was best protected when the shield was positioned on his left side.For the assistant operator, the optimal protection was obtained when the shield was positioned close to him in both PA and left lateral projection.In the optimal position of ceiling-suspended lead shield, the highest radiation dose rate (0.71 mSv/h in glass group and 1.07 mSv/h in mixed group) was recorded on the principal operator at the height of 120 cm at PA projection, and higher radiation dose rate (≥0.47 mSv/h) was recorded on every point of both operators at the left lateral projection.Meanwhile, the overall received radiation doses of the two groups were very close.At the principal operator standing area, except for the position of 120 cm height (attenuation ratio 60.11% in glass group and 39.89% in mixed group), the attenuation ratio of each measuring point was above 93%.And the assistant operator standing area the attenuation ratio was 57%-97%.The lateral shielding ratio was generally slightly higher than PA shielding ratio.Conclusion The radiation protection effect of the two type shields is quite similar, both shields can obtain excellent protection efficacy.But the radiation dose at the height of 120 cm above the ground at PA projection is higher for the principal operator, while at lateral projection the radiation dose at all height levels is still relatively higher for both operators.Therefore, the radiation protection at the level of 120 cm height needs to be strengthened and the lateral projection exposure should be used as less as possible.