Fundamental Limitations on Electron Molecular Microscopy

Author(s):  
George T. Trammell ◽  
James R. Breedlove

We consider the feasibility of an electron “molecular microscope” which could be used to determine the structure of a biological molecule by forming an image in which its individual atoms are resolved.Each atom which is imaged must scatter at least one electron. (This is true irrespective of the imaging technique so long as the images of neighboring atoms are resolved.) While we may ignore the effects of the elastically scattered electrons on the molecular structure, inelastic collisions will lead (with a certain probability) to molecular dissociation or rearrangement. The “image” formed will thus be a composite picture of the molecule over the history of its irradiation and may bear little relation to the original molecular structure, and this is a fundamental “Limitation on molecular microscopy.

Biology ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 394
Author(s):  
Elmira I. Yakupova ◽  
Liya G. Bobyleva ◽  
Sergey A. Shumeyko ◽  
Ivan M. Vikhlyantsev ◽  
Alexander G. Bobylev

Proteins can perform their specific function due to their molecular structure. Partial or complete unfolding of the polypeptide chain may lead to the misfolding and aggregation of proteins in turn, resulting in the formation of different structures such as amyloid aggregates. Amyloids are rigid protein aggregates with the cross-β structure, resistant to most solvents and proteases. Because of their resistance to proteolysis, amyloid aggregates formed in the organism accumulate in tissues, promoting the development of various diseases called amyloidosis, for instance Alzheimer’s diseases (AD). According to the main hypothesis, it is considered that the cause of AD is the formation and accumulation of amyloid plaques of Aβ. That is why Aβ-amyloid is the most studied representative of amyloids. Therefore, in this review, special attention is paid to the history of Aβ-amyloid toxicity. We note the main problems with anti-amyloid therapy and write about new views on amyloids that can play positive roles in the different organisms including humans.


2013 ◽  
Vol 39 (6) ◽  
pp. 742-746 ◽  
Author(s):  
Liégina Silveira Marinho ◽  
Nathalia Parente de Sousa ◽  
Carlos Augusto Barbosa da Silveira Barros ◽  
Marcelo Silveira Matias ◽  
Luana Torres Monteiro ◽  
...  

Bronchial stenosis can impair regional lung ventilation by causing abnormal, asymmetric airflow limitation. Electrical impedance tomography (EIT) is an imaging technique that allows the assessment of regional lung ventilation and therefore complements the functional assessment of the lungs. We report the case of a patient with left unilateral bronchial stenosis and a history of tuberculosis, in whom regional lung ventilation was assessed by EIT. The EIT results were compared with those obtained by ventilation/perfusion radionuclide imaging. The patient was using nasal continuous positive airway pressure (CPAP) for the treatment of obstructive sleep apnea syndrome. Therefore, we studied the effects of postural changes and of the use of nasal CPAP. The EIT revealed heterogeneous distribution of regional lung ventilation, the ventilation being higher in the right lung, and this distribution was influenced by postural changes and CPAP use. The EIT assessment of regional lung ventilation produced results similar to those obtained with the radionuclide imaging technique and had the advantage of providing a dynamic evaluation without radiation exposure.


Brain Injury ◽  
2018 ◽  
Vol 32 (10) ◽  
pp. 1255-1264 ◽  
Author(s):  
Sarah M. Jurick ◽  
Samantha N. Hoffman ◽  
Scott Sorg ◽  
Amber V. Keller ◽  
Nicole D. Evangelista ◽  
...  

Author(s):  
Letícia Do Prado

 ResumoDorothy Crowfoot Hodgkin formou-se em química pela Somerville Oxford, doutorou-se em Cambridge e liderou o grupo de pesquisa que decifrou a estrutura molecular de várias moléculas biológicas complexas como: a penicilina, a vitamina B12 e a insulina. Seu nome não foi tão ovacionado quanto o de outros ganhadores do Prêmio Nobel já que seu método de trabalho, a cristalografia de raio X para a análise de moléculas complexas era ainda pioneiro e pouco disseminado entre os laboratórios da época. Foi a busca de soluções exatas para problemas difíceis que motivaram Dorothy a superar tempos de guerra, contratempos experimentais, demandas do casamento, da maternidade e a dor física persistente, para se tornar uma das maiores cientistas do século. Neste trabalho apresentaremos brevemente a vida de Dorothy, sua infância distante dos pais e rica em experiências culturais, sua juventude, as dificuldades que precederam sua entrada na Universidade e sua vida como pesquisadora, e mais especificamente, falaremos sobre sua colaboração para a solução da estrutura molecular da penicilina no cenário da Segunda Guerra Mundial. Nosso objetivo é apresentar ao leitor o trabalho de Dorothy ancorados em suas  publicações originais e suas biografias, de maneira a contribuir com a disseminação da história das mulheres na ciência. Palavras-chave: Dorothy Crowfoot Hodgkin; Penicilina; Mulheres na Ciência.AbstractDorothy Crowfoot Hodgkin graduated in chemistry from Somerville Oxford, doctorate from Cambridge and led the research group that deciphered the molecular structure of several complex biological molecules such as penicillin, vitamin B12 and insulin. Her name was not as ovation as that of other Nobel Prize winners since their method of working, X-ray crystallography for the analysis of complex molecules was still pioneering and little disseminated among laboratories of the time. It was the search for exact solutions to difficult problems that motivated Dorothy to overcome wartime, experimental setbacks, marriage demands, maternity, and persistent physical pain to become one of the greatest scientists of the century. In this work we will briefly present the life of Dorothy, her childhood far from her parents and rich in cultural experiences, her youth and the difficulties that preceded her entrance into the University and her life as a researcher, and more specifically, we will talk about her collaboration for the solution of molecular structure of penicillin in the scene of World War II. Our goal is to present the Doroty works, anchored in her original published and her biographies in order to contribute with the dissemination of history of women in science.Keywords: Dorothy Crowfoot Hodgkin; Penicillin; Women in Science.


1998 ◽  
Vol 12 (03) ◽  
pp. 309-360
Author(s):  
Toshio Kawai

The Titius–Bode law governs the planet distribution in our Solar system. In this paper a possible explanation is proposed based on inelastic collision effects among planetessimals during the evolution of the Solar system. The main purpose of this paper is, however, to introduce a strategy to study phenomena driven by rare but drastic events such as colllisions in the planetary problem. Many complex systems evolve through rare but violent events, so that an efficient strategy to simulate such systems is desirable. An event-driven strategy is proposed in this article, and is used to produce many runs of 108 year evolution history of planetary systems. I have found that the Titius–Bode law holds approximately, if the gravitational effect (scattering) and the collisions are taken into account. The result illustrates the importance of inelastic collisions, which are often neglected in the standard classical mechanics courses. Therefore, for completeness, other simpler particle systems under the effect of inelastc collisions, such as one-dimensional systems, are also included.


1993 ◽  
Vol 9 (3) ◽  
pp. 335-345 ◽  
Author(s):  
Stuart S. Blume

AbstractEach group involved in the development of a new medical technology constantly assesses the value of the emergent technique in terms of the group’s own specific goals and conventions. The history of infrared thermography demonstrates the social nature of this assessment process.


The history of high-resolution n.m.r. in solids has been, inter alia , a quest for narrow spectral lines. Yet, with few exceptions, solid state resonances have not been sharpened to the degree of liquid resonances. To aid in the appraisal of the status of n.m.r. in solids, we identify and summarize, for the particular case of 13 C n.m.r. in organic solids, those effects that can degrade resolution. Some of these mechanisms are under the experimenter’s control; for example, certain are exacerbated at high magnetic field. Others, however, represent fundamental limitations imposed by the specimen and are valid reflections of the complexity of a solid as contrasted to a liquid. In solids, magnetic dipolar spin-spin couplings can not only degrade resolution but also complicate, hopelessly in some cases, the determination of spin-lattice relaxation rates from which one seeks information about molecular motions. The consequences of this competition between spin-spin and spin-lattice effects are examined, as well as criteria and strategies to isolate the motional contributions to relaxation rates.


2012 ◽  
Vol 2012 ◽  
pp. 1-3
Author(s):  
Miguel Angel Ramirez-Marrero ◽  
Manuel de Mora-Martin

Congenital cardiopathies in adults are a rare clinical entity in the cardiology consultations. Advances in imaging techniques allow the fortuitous diagnosis of mild forms of these congenital abnormalities. We describe a case of an asymptomatic 41-year-old man, with a medical history of recurrent pneumonia during childhood and an established diagnosis of scimitar syndrome by computed tomography.


Author(s):  
Gordon I Ogilvie

Maxwell's investigations into the stability of Saturn's rings provide one of the earliest analyses of the dynamics of astrophysical discs. Current research in planetary rings extends Maxwell's kinetic theory to treat dense granular gases of particles undergoing moderately frequent inelastic collisions. Rather than disrupting the rings, local instabilities may be responsible for generating their irregular radial structure. Accretion discs around black holes or compact stars consist of a plasma permeated by a tangled magnetic field and may be compared with laboratory fluids through an analogy that connects Maxwell's researches in electromagnetism and viscoelasticity. A common theme in this work is the appearance of a complex fluid with a dynamical constitutive equation relating the stress in the medium to the history of its deformation.


2018 ◽  
Vol 88 (1) ◽  
Author(s):  
Dimitrios Papadopoulos ◽  
Panagiotis Misthos ◽  
Maria Chorti ◽  
Vlasios Skopas ◽  
Alexandra Nakou ◽  
...  

Pulmonary hypoplasia (PH) is a developmental anomaly of the lung parenchyma, characterized by a decrease in the number and size of airways, alveoli and vessels. We present a case of a 31-year-old patient with a history of chronic productive cough and frequent respiratory infections, who was referred for investigation of abnormal chest x-ray. The combination of chest computed tomography (CT) and bronchoscopy set the diagnosis of left pulmonary hypoplasia and the patient was treated surgically with a left pneumonectomy. PH is usually diagnosed immediately after birth, causing severe respiratory failure with high mortality. The less severe, unilateral forms can possibly survive by causing compensatory hyperinflation of the other lung and remain undiagnosed until adulthood, presenting either asymptomatic or with symptoms of chronic bronchitis and recurrent respiratory infections. Chest CT is considered the imaging technique of choice for the diagnosis and for the differential diagnosis from other congenital or acquired conditions. The treatment is usually conservative, although surgical resection is indicated in cases of severe cystic changes and intense symptomatology.


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