130,751 research outputs found
Isothiazoles. Part II. Reaction of d-diethylamino-4-(4-methoxyphenyl)-isothiazole-1,1-dioxide with sodium azide.
No full text3-Diethylamino-4-(4-methoxyphenyl)-isothiazole-1,1-dioxide 1, was reacted with azide ion in different solvents. Depending on reaction conditions 4-diethylamino-3a,6a-dihydro-3a-(4-methoxyphenyl)-1H-isothiazole-[4,5 -d]-1,2,3-triazole-6,6-dioxide 3 and/or 4-diethylamino-1-[3-diethylamino-4,5-dihydro-4-(4-methoxyphenyl)-5-is othiazolyl-1,1-dioxide]-3a,6a-dihydro-3a-(4-methoxyphenyl)-1H-isothia zole-[4,5-d]-1,2,3- triazole-6,6-dioxide 4 were formed. When ethanol or acetone were used as reaction solvent the formation of the above the compounds was accompanied by solvent addition forming 3-diethylamino-4,5-dihydro-4-(4-methoxyphenyl)-5-ethoxy-isothiazole-1 ,1-dioxide 6, respectively. Reaction mechanisms and structures of products are discussed
Decline of protein structure rigidity with interatomic distance
No full textAbstract Background Protein structural rigidity was analyzed in a non-redundant ensemble of high-resolution protein crystal structures by means of the Hirshfeld test, according to which the components (uX and uY) of the B-factors of two atoms (X and Y) along the interatomic direction is related to their degree of rigidity: the atoms may move as a rigid body if uX = uY and they cannot if uX ≠ uY. Results It was observed that the rigidity degree diminishes if the number of covalent bonds intercalated between the two atoms (d_seq) increases, while it is rather independent on the Euclidean distance between the two atoms (d): for a given value of d_seq, the difference between uX and uY does not depend on d. No additional rigidity decline is observed when d_seq ≥ ~ 30 and this upper limit is very modest, close to 0.015 Å. Conclusions This suggests that protein flexibility is not fully described by B-factors that capture only partially the wide range of distortions that proteins can afford
Half a century of Ramachandran plots
No full textOn the occasion of their fiftieth birthday, it is opportune to
review the first half century of Ramachandran plots. In the
present review, some of the most relevant aspects of this
fifty-year history are summarized, from the original ideas of
Gopalasamudram Narayana Ramachandran to subsequent
revisions and to applications in structural biology. This will
not be a guided walk through five decades of Ramachandran
plots, but a commented summary of the lines along which the
original ideas evolved and continue to develop, and of their
applications
B-factor accuracy in protein crystal structures
No full textThe accuracy of B factors in protein crystal structures has been determined by comparing the same atoms in numerous, independent crystal structures of Gallus gallus lysozyme. Both B-factor absolute differences and normal probability plots indicate that the estimated B-factor errors are quite large, close to 9 Å2 in ambient-temperature structures and to 6 Å2 in low-temperature structures, and surprisingly are comparable to values estimated two decades ago. It is well known that B factors are not due to local movements only but reflect several, additional factors from crystal defects, large-scale disorder, diffraction data quality etc. It therefore remains essential to normalize B factors when comparing different crystal structures, although it has clearly been shown that they provide useful information about protein dynamics. Improved, quantitative analyses of raw B factors require novel experimental and computational tools that are able to disaggregate local movements from other features and properties that affect B factors
Isothiazoles. Part II. Reaction of 3-diethylamino-4-(4-methoxyphenyl)-isothiazole-1,1-dioxide with sodium azide
No full text
Pain perception using a computer-controlled anaesthetic delivery system in paediatric dentistry : A review
No full textAim In paediatric dentistry it is essentials to reduce axiety and fear induced by local anaesthetic injection, in order to obtain patient's cooperation and achieve a successful treatment. Hence, this review is aiming to primary evaluate pain perception in paediatric patients when using a computer-controlled local anaesthetic delivery system (C-CLADS) compared to traditional injection. Methods A database literature search was conducted on both MEDLINE and Cochrane Central Register of Controlled Trials and a data extraction table was created to perform a critical evaluation of each scientific article. The primary results were the perception of pain during anaesthesia and the patient's behaviour, the secondary the amount of anaesthetic required and its duration over time. Results In the review were included 7 clinical studies regarding paediatric patients where split-mouth designs or group division were used. The age range was between 5 and 17 years old. Pain and fear parameters were measured by visual analogue scales, behavioural scales, heart rate and satisfaction questionnaires. Conclusions Substantial heterogeneity between clinical trials was observed, which led to difficult comparison. Computerised devices have proved to be interesting in reducing pain during anaesthesia, improving the approach to the paediatric patient. It is advisable to conduct research with anxious subjects and patients under the age of 4, because no evidence has been found in the literature. It is recommended to conduct further research with anxious subjects and patients below the age of 4, where Relative Analgesia by Langa or pharmacological anxiolysis are frequently used
Microfluidic and lab-on-a-chip preparation routes for organic nanoparticles and vesicular systems for nanomedicine applications
No full textIn recent years, advancements in the fields of microfluidic and lab-on-a-chip technologies have provided unique opportunities for the implementation of nanomaterial production processes owing to the miniaturisation of the fluidic environment. It has been demonstrated that microfluidic reactors offer a range of advantages compared to conventional batch reactors, including improved controllability and uniformity of nanomaterial characteristics. In addition, the fast mixing achieved within microchannels, and the predictability of the laminar flow conditions,can be leveraged to investigate the nanomaterial formation dynamics. In this article recent developments in the field of microfluidic production of nanomaterials for drug delivery applications are reviewed. The features that make microfluidic reactors a suitable technological platform are discussed in terms of controllability of nanomaterials production. An overview of the various strategies developed for the production of organic nanoparticles and colloidal assemblies is presented, focusing on those nanomaterials that could have an impact on nanomedicine field such as drug nanoparticles, polymeric micelles, liposomes, polymersomes, polyplexes and hybrid nanoparticles. The effect of microfluidic environment on nanomaterials formation dynamics, as well as the use of microdevices as tools for nanomaterial investigation is also discussed
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