On the interaction of azithromycin monohydrate with metallic containers

2006 ◽  
Vol 39 (6) ◽  
pp. 826-830 ◽  
Author(s):  
J. Montejo-Bernardo ◽  
S. García-Granda ◽  
M. Bayod-Jasanada ◽  
I. Llorente ◽  
L. Llavona
Keyword(s):  
Crystal Form ◽  
Crystal Habit ◽  
Metallic Surfaces ◽  
Crystal Face ◽  
Great Propensity ◽  
Erythromycin A ◽  
Semisynthetic Derivative

The monohydrate form of azithromycin (an antibiotic semisynthetic derivative of erythromycin A) is difficult to manipulate due to its great propensity to stick to metallic surfaces (during crystallization, drying, grinding,etc.). In this paper, this behaviour is explained on the basis of the conformation and packing of the azithromycin molecules in this crystal form. In particular, the crystal habit favours interaction between the N and O atoms with the metal through one particular crystal face.

Fundamentals

2020 ◽  
pp. 41-77
Author(s):  
Joel Bernstein
Keyword(s):  
Fusion Rule ◽  
Crystal Form ◽  
Crystal Habit ◽  
Heat Of Fusion ◽  
Transition Rule ◽  
Phase Rule ◽  
Entropy Of Fusion ◽  
Thermodynamic Relationships ◽  
Heat Of Transition ◽  
Definition Of

The physical and structural fundamentals of polymorphism are introduced, including a review of the phase rule and the thermodynamic relations in polymorphs. The latter are used to introduce energy–temperature diagrams, leading to the definition of the concepts enantiotropism and monotropism describing the thermodynamic relationships between and among polymorphs with appropriate examples. The alternate representation of phase diagram in terms of pressure and temperature is also presented. These lead to a number of rules regarding the relationships between polymorphs and ways to understand and predict some important physical properties: the heat-of-transition rule, the heat-of-fusion rule, the entropy-of-fusion rule, the heat-capacity rule, the density rule, and the infrared rule. Structural aspects include the distinction between crystal form and crystal habit and methods for characterizing and comparing structures in polymorphic systems. Current developments are discussed that deal with the ramifications of nanoscale situations on structural concepts and thermodynamic relationships.

Low-Voltage scanning electron microscope (LVSEM) determination of nevirapine Crystal Habit in a Pharmaceutical Suspension

1992 ◽  
Vol 50 (2) ◽  
pp. 1326-1327
Author(s):  
A. Angel ◽  
R. Peischl ◽  
A. Hawi
Keyword(s):  
Low Voltage ◽  
Aqueous Suspension ◽  
High Surface ◽  
High Surface Area ◽  
Crystal Form ◽  
Transcriptase Inhibitor ◽  
Crystal Habit ◽  
Stable Form ◽  
Subsequent Conversion ◽  
Reverse Transcriptase Inhibitor

LVSEM permits the examination of materials with reduced radiation damage and high contrast, factors which are critical to the successful examination of organic crystals. In this study, LVSEM was applied to characterize the structure of a beam sensitive anhydrous crystal form and its subsequent conversion to the hemihydrate form in an aqueous suspension.Nevirapine, a dipyridodiazepenone compound, is a reverse transcriptase inhibitor currently being developed for the treatment of AIDS. Nevirapine exists as the hemihydrate stable form and as the anhydrous metastable form. The hemihydrate crystals are multifaceted blades (Fig. 1) whereas the anhydrous form exists predominately as large agglomerates of porous “coral like” crystals with high surface area (Fig. 2). When formulated in aqueous suspensions, anhydrous Nevirapine converted into the hemihydrate form, with eventual growth of the hemihydrate crystals. The extent of conversion and rate of growth have been determined to be a function of temperature and time. LVSEM was used to study the anhydrous-to-hemihydrate conversion as the two forms could easily be identified by their characteristic morphology.

scholarly journals Recrystallization and Production of Spherical Submicron Particles of Sulfasalazine Using a Supercritical Antisolvent Process

Crystals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 295
Author(s):  
Wei-Yi Wu ◽  
Chie-Shaan Su
Keyword(s):  
Solid State ◽  
Solution Concentration ◽  
Crystal Form ◽  
Lower Solution ◽  
Nozzle Diameter ◽  
Submicron Particles ◽  
Spherical Particles ◽  
Crystal Habit ◽  
Operating Pressure ◽  
Supercritical Antisolvent

In this study, the recrystallization and production of spherical submicron particles of sulfasalazine, an active pharmaceutical ingredient (API), were performed using the supercritical antisolvent (SAS) process, a nonconventional crystallization technique. Sulfasalazine was dissolved in tetrahydrofuran (THF), and supercritical carbon dioxide (CO2) served as the antisolvent. The effects of operating parameters on the SAS process, including the operating pressure, solution concentration, solution flowrate, CO2 flowrate, and spraying nozzle diameter, at two operating temperatures were examined. The solid-state characteristics of sulfasalazine before and after the SAS process, including particle size, crystal habit, and crystal form, were analyzed using a scanning electron microscope (SEM), powder X-ray diffractometer (PXRD), and differential scanning calorimeter (DSC). A higher operating temperature, intermediate operating pressure, higher CO2 flowrate, and lower solution flowrate are recommended to obtain spherical particles of sulfasalazine. The effects of the solution concentration and spraying nozzle diameter on the SAS process were negligible. Under optimal conditions, spherical sulfasalazine crystals with a mean size of 0.91 μm were generated, and this study demonstrated the feasibility for tuning the solid-state characteristics of API through the SAS process.

scholarly journals Application of Box–Behnken Design to Investigate the Effect of Process Parameters on the Microparticle Production of Ethenzamide through the Rapid Expansion of the Supercritical Solutions Process

Pharmaceutics ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 42 ◽  
Author(s):  
Yung-Tai Hsu ◽  
Chie-Shaan Su
Keyword(s):  
Thermal Behavior ◽  
Process Parameters ◽  
Crystal Form ◽  
Rapid Expansion ◽  
Crystal Habit ◽  
Extraction Temperature ◽  
Box Behnken Design ◽  
Mean Size ◽  
Supercritical Solutions ◽  
Expansion Temperature

In this study, the rapid expansion of the supercritical solutions (RESS) process was used to produce microparticles of a commonly used anti-inflammatory drug, ethenzamide. The effects of process parameters in RESS including the extraction temperature, pre-expansion temperature, and post-expansion temperature were investigated using the Box–Behnken design. According to the results of the analysis of variance (ANOVA), the effect of pre-expansion temperature is the most significant parameter on the mean size of RESS-produced ethenzamide. A higher pre-expansion temperature benefits the production of smaller crystals. In addition, a quadratic effect of the post-expansion temperature was also identified. Through RESS, ethenzamide microparticles with a mean size of 1.6 μm were successfully produced. The solid-state properties including the crystal habit, crystal form, thermal behavior, and spectrometric property were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR), differential scanning calorimeter (DSC), and powder X-ray diffraction (PXRD). These analytical results show that the rod-like crystals were generated through RESS, and the crystal form, thermal behavior, and spectrometric property of RESS-produced crystals are consistent with the unprocessed ethenzamide.

The native structure of the eukaryotic ribosome

1983 ◽  
Vol 41 ◽  
pp. 432-433
Author(s):  
R.A. Milligan ◽  
P.N.T. Unwin
Keyword(s):  
Ribosomal Proteins ◽  
Crystal Form ◽  
Native Structure ◽  
X Ray Diffraction ◽  
Eukaryotic Ribosome ◽  
Vitro Analysis ◽  
In Vitro Analysis ◽  
Resolution Structure ◽  
Stable Unit

A detailed understanding of the mechanism of protein synthesis will ultimately depend on knowledge of the native structure of the ribosome. Towards this end we have investigated the low resolution structure of the eukaryotic ribosome embedded in frozen buffer, making use of a system in which the ribosomes crystallize naturally.The ribosomes in the cells of early chicken embryos form crystalline arrays when the embryos are cooled at 4°C. We have developed methods to isolate the stable unit of these arrays, the ribosome tetramer, and have determined conditions for the growth of two-dimensional crystals in vitro, Analysis of the proteins in the crystals by 2-D gel electrophoresis demonstrates the presence of all ribosomal proteins normally found in polysomes. There are in addition, four proteins which may facilitate crystallization. The crystals are built from two oppositely facing P4 layers and the predominant crystal form, accounting for >80% of the crystals, has the tetragonal space group P4212, X-ray diffraction of crystal pellets demonstrates that crystalline order extends to ~ 60Å.

Ultrastructural autoradiography of L6 skeletal-muscle cells exposed to a tritiated macrolide antibiotic (LY237216) in vitro

1992 ◽  
Vol 50 (1) ◽  
pp. 612-613
Author(s):  
S.L. White ◽  
C.B. Jensen ◽  
D.D. Giera ◽  
D.A. Laska ◽  
M.N. Novilla ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Quantitative Analysis ◽  
Macrolide Antibiotic ◽  
Circle Method ◽  
Apical Surface ◽  
Polycarbonate Membrane ◽  
L6 Cells ◽  
Low Viscosity ◽  
Erythromycin A

In vitro exposure to LY237216 (9-Deoxo-11-deoxy-9,11-{imino[2-(2-methoxyethoxy)ethylidene]-oxy}-(9S)-erythromycin), a macrolide antibiotic, was found to induce cytoplasmic vacuolation in L6 skeletal muscle myoblast cultures (White, S.L., unpubl). The present study was done to determine, by autoradiographic quantitative analysis, the subcellular distribution of 3H-LY237216 in L6 cells.L6 cells (ATCC, CRL 1458) were cultured to confluency on polycarbonate membrane filters (Millipore Corp., Bedford, MA) in M-199 medium (GIBCO® Labs) with 10% fetal bovine serum. The cells were exposed from the apical surface for 1-hour to unlabelled-compound (0 μCi/ml) or 50 (μCi/ml of 3H-LY237216 at a compound concentration of 0.25 mg/ml. Following a rapid rinse in compound-free growth medium, the cells were slam-frozen against a liquid nitrogen cooled, polished copper block in a CF-100 cryofixation unit (LifeCell Corp., The Woodlands, TX). Specimens were dried in the MDD-C Molecular Distillation Drier (LifeCell Corp.), vapor osmicated and embedded in Spurrs low viscosity resin. Ultrathin sections collected on formvar coated stainless steel grids were counter-stained, then individually mounted on corks. A monolayer of Ilford L4 nuclear emulsion (Polysciences, Inc., Warrington, PA) was placed on the sections, utilizing a modified “loop method”. The emulsions were exposed for 7-weeks in a light-tight box at 4°C. Autoradiographs were developed in Microdol-X developer and examined on a Philips EM410LS transmission electron microscope. Quantitative analysis of compound localization employed the point and circle approach of Williams; incorporating the probability circle method of Salpeter and McHenry.

A potent cytotoxic semisynthetic derivative of perezone with phenylglycine

Planta Medica ◽  
2006 ◽  
Vol 72 (11) ◽  
Author(s):  
RG Enríquez ◽  
D Alonso-Cortés ◽  
MC Lozada ◽  
EV Avila ◽  
JL Montiel ◽  
...  
Keyword(s):  
Semisynthetic Derivative

Теория гетерогенного катализа. Теория хемосорбции

2021 ◽  
Author(s):  
Василий Садовников
Keyword(s):  
Heterogeneous Catalysis ◽  
Potential Energy ◽  
Publishing House ◽  
Cell Number ◽  
Oil Refining ◽  
Lateral Interaction ◽  
Reaction Products ◽  
Crystal Face ◽  
Independent Particle ◽  
The Face

This monograph is a continuation of the monograph by V.V. Sadovnikov. Lateral interaction. Moscow 2006. Publishing house "Anta-Eco", 2006. ISBN 5-9730-0017-6. In this work, the foundations of the theory of heterogeneous catalysis and the theory of chemisorption are more easily formulated. The book consists of two parts, closely related to each other. These are the theoretical foundations of heterogeneous catalysis and chemisorption. In the theory of heterogeneous catalysis, an experiment is described in detail, which must be carried out in order to isolate the stages of a catalytic reaction, to find the stoichiometry of each of the stages. This experiment is based on the need to obtain the exact value of the specific surface area of the catalyst, the number of centers at which the reaction proceeds, and the output curves of each of the reaction products. The procedures for obtaining this data are described in detail. Equations are proposed and solved that allow calculating the kinetic parameters of the nonequilibrium stage and the thermodynamic parameters of the equilibrium stage. The description of the quantitative theory of chemisorption is based on the description of the motion of an atom along a crystal face. The axioms on which this mathematics should be based are formulated, the mathematical apparatus of the theory is written and the most detailed instructions on how to use it are presented. The first axiom: an atom, moving along the surface, is present only in places with minima of potential energy. The second axiom: the face of an atom is divided into cells, and the position of the atom on the surface of the face is set by one parameter: the cell number. The third axiom: the atom interacts with the surrounding material bodies only at the points of minimum potential energy. The fourth axiom: the solution of the equations is a map of the arrangement of atoms on the surface. The fifth axiom: quantitative equations are based on the concept of a statistically independent particle. The formation energies of these particles and their concentration are calculated by the developed program. The program based on these axioms allows you to simulate and calculate the interaction energies of atoms on any crystal face. The monograph is intended for students, post-graduate students and researchers studying work and working in petrochemistry and oil refining.

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