Microscopic motility of isolated E. coli flagella

The fluctuation-dissipation theorem describes the intimate connection between the Brownian diffusion of thermal particles and their drag coefficients. In the simple case of spherical particles, it takes the form of the Stokes-Einstein relationship that links the particle geometry, fluid viscosity, and diffusive behavior. However, studying the fundamental properties of microscopic asymmetric particles, such as the helical-shaped propeller used by $\textit{E. coli}$, has remained out of reach for experimental approaches due to the need to quantify correlated translation and rotation simultaneously with sufficient spatial and temporal resolution. To solve this outstanding problem, we generated volumetric movies of fluorophore-labeled, freely diffusing, isolated $\textit{E. Coli}$ flagella using oblique plane microscopy. From these movies, we extracted trajectories and determined the hydrodynamic propulsion matrix directly from the diffusion of flagella via a generalized Einstein relation. Our results validate prior proposals, based on macroscopic wire helices and low Reynolds number scaling laws, that the average flagellum is a highly inefficient propeller. Specifically, we found the maximum propulsion efficiency of flagella is less than 5%. Beyond extending Brownian motion analysis to asymmetric 3D particles, our approach opens new avenues to study the propulsion matrix of particles in complex environments where direct hydrodynamic approaches are not feasible.Comment: 6 pages, 4 figures, 9 supplemental sections, 7 supplemental figures, 3 supplemental movies *authors contributed equally and reserve the right to change order for first authorshi

A green approach for the quantification of daptomycin in pharmaceutical formulation by UV spectrophotometry

abstract Daptomycin is the first approved drug from a new class of antimicrobials, the cyclic lipopeptides, and is a very important antimicrobial agent in current clinical practice. Currently, there are no "green" analytical methods described in the literature to analyze the typical pharmaceutical dosage form of daptomycin. Thus, the aim of this work was to validate an environment-friendly spectrophotometric method in the UV region, for the analysis of daptomycin as a lyophilized powder. Water was used as diluent and the analyses were carried out on a spectrophotometer at 221 nm. The method met all validation requirements of the ICH guidelines, over a concentration range of 6-21 µg mL-1. A Student's t-test demonstrated that the proposed method was comparable to an HPLC method previously validated. Thus, the validated spectrophotometric method could quantify daptomycin in a powder form for injectable solutions, while being an economical, rapid, and "green" alternative for routine analysis in quality control

Polymorphism: an evaluation of the potential risk to the quality of drug products from the Farmácia Popular Rede Própria

Polymorphism in solids is a common phenomenon in drugs, which can lead to compromised quality due to changes in their physicochemical properties, particularly solubility, and, therefore, reduce bioavailability. Herein, a bibliographic survey was performed based on key issues and studies related to polymorphism in active pharmaceutical ingredient (APIs) present in medications from the Farmácia Popular Rede Própria. Polymorphism must be controlled to prevent possible ineffective therapy and/or improper dosage. Few mandatory tests for the identification and control of polymorphism in medications are currently available, which can result in serious public health concerns

Conformational Polymorphism in Racemic Crystals of the Diuretic Drug Chlortalidone

Chlortalidone (HIGROTON) is a diuretic drug widely used in antihypertensive therapy. Thus far, only two solid-state polymorphs of chlortalidone have been reported. We elucidated the structure of chlortalidone form I and a new polymorph. This new phase, namely, chlortalidone form III, was also entirely characterized. It was possible to conclude that it is a conformer with a different orientation of the chlorobenzenesulfonamide moiety. Compared to form I, it has a rotation of about 90 degrees on the axis of the C-C bond bridging the substituted phenyl and isoindolinyl rings. This conformational feature is related to the crystal packing patterns of the chlortalidone forms. Furthermore, certain intermolecular hydrogen bonds are present in both polymorphs, giving rise to ribbons with chlortalidone enantiomers alternately placed into them. The chlortalidone form I and form III crystallize in the triclinic space group P (1) over bar as racemic mixtures. Additional conformational details also differentiate the chlortalidone conformers. Slight twists on the isoindolinyl and sulfamyl groups exist. Considering all structural relationships, the fingerprint plots derived from the Hirshfeld surfaces exhibited the characteristics of the chlortalidone form I and form III crystal structures.Brazilian Research Council CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP (Fundacao de Amparo Pesquisa do Estado de Sao Paulo)FAPEMIG (Fundacao de Amparo A Pesquisa do Estado de Minas Gerais)Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Ministerio da Saude of Brazil[EDT-3310/06]Ministerio da Saude of BrazilMinisterio da Saude of Brazil[APQ-2011-5.02/07]Ministerio da Saude of BrazilMinisterio da Saude of BrazilMinisterio da Saude of Brazil[APQ-6010-5.02/07

Solubility and dissolution studies of tibolone polymorphs

ABSTRACT Different solid forms of an active pharmaceutical ingredient can have distinct chemical and physical characteristics. In this work, we studied the solubility and dissolution properties of the described tibolone polymorphic forms (I and II). Both forms were successively recrystallized and characterized by powder X-ray diffraction and attenuated total reflection infrared spectroscopy. Equilibrium solubility and dissolution profiles were performed for both forms. Solubility studies demonstrated that form II is statistically more soluble in water, 0.01 mol L-1 HCl and pH 4.5 acetate buffer. The solubility of forms I and II were explained in terms of crystal packing. Dissolution tests of tablets showed a lower release of polymorphic form II than form I from tablets. The results showed an impact of polymorphism on the quality of tibolone tablets and suggest that tibolone forms I and II can show distinct interactions with pharmaceutical excipients used in tablets. Therefore, only form I is acceptable for the preparation of tablet forms. Based on our results, we propose the quality control on tibolone raw materials using X-ray diffraction analysis and attenuated total reflection infrared spectroscopy

Dissolution test optimization for meloxicam in the tablet pharmaceutical form

Meloxicam is a broadly used drug in the therapeutics for the osteoarthritis and rheumatoid arthritis treatments in adults, and it is available in the Brazilian market, as tablet and capsule pharmaceutical forms. The present work aimed to establish conditions for accomplishment of the dissolution test of 15 mg meloxicam tablets (A and B test products), compared with the reference product, since there is no monograph about dissolution assays for meloxicam in official summaries. To optimize the conditions several parameters were tested and, according to obtained results, the use of pH 7.5 phosphate buffer (900mL, at 37 ± 0.5ºC) as dissolution medium, paddle method (apparatus 2), stirring speed of the dissolution medium at 100 rpm and collect time of 60 minutes were considered satisfactory. The samples were quantified by UV spectrophotometric method at 362 nm. The products presented kinetics of first-order. Dissolution efficiency values were of 83.25, 83.73 and 88.10% for the A, B and reference products, respectively. Factors f1 and f2 were calculated and similarity of the tested medicines was demonstrated. The dissolution test was validated presenting selectivity, linearity, precision and accuracy within of the acceptance criteria.<br>O meloxicam é fármaco amplamente utilizado na terapêutica para o tratamento de osteoartrite e artrite reumatóide em adultos, e encontra-se disponível no mercado brasileiro, sob as formas farmacêuticas comprimido e cápsula. O presente trabalho objetivou estabelecer condições para realização do teste de dissolução de meloxicam 15 mg na forma farmacêutica comprimido (medicamentos-teste A e B), comparado com o medicamento de referência, visto que não há monografia para o ensaio de dissolução com meloxicam em compêndios oficiais. Para otimização das condições, diversos parâmetros foram testados e de acordo com os resultados obtidos, a utilização de tampão fosfato pH 7,5 (900mL, a 37 ± 0,5 ºC) como meio de dissolução, aparato 2 (pá), velocidade de agitação do meio de dissolução de 100 rpm e tempo de coleta em 60 minutos, foram considerados satisfatórios. As amostras foram quantificadas por espectrofotometria na região do ultravioleta, a 362 nm. Os produtos apresentaram cinética de primeira ordem. Para a eficiência de dissolução encontraram-se valores de 83,25, 83,73 e 88,10% para os medicamentos-teste A e B e referência, respectivamente. Os fatores f1 e f2 foram calculados, demonstrando haver similaridade entre os medicamentos avaliados. O ensaio de dissolução foi validado apresentando seletividade, linearidade, precisão e exatidão dentro dos critérios de aceitação