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1.
J Chem Phys ; 151(14): 144901, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31615257

RESUMO

We demonstrate that nascent polymer crystals (i.e., nuclei) are anisotropic entities with neither spherical nor cylindrical geometry, in contrast to previous assumptions. In fact, cylindrical, spherical, and other high symmetry geometries are thermodynamically unfavorable. Moreover, postcritical transitions are necessary to achieve the lamellae that ultimately arise during the crystallization of semicrystalline polymers. We also highlight how inaccurate treatments of polymer nucleation can lead to substantial errors (e.g., orders of magnitude discrepancies in predicted nucleation rates). These insights are based on quantitative analysis of over four million crystal clusters from the crystallization of prototypical entangled polyethylene melts. New comprehensive bottom-up models are needed to capture polymer nucleation.


Assuntos
Polietileno/química , Cristalização , Conformação Molecular , Simulação de Dinâmica Molecular , Termodinâmica
2.
Phys Chem Chem Phys ; 21(41): 22763-22773, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31595279

RESUMO

The adenosine A1 receptor (A1R) is one of four adenosine receptors in humans, which are involved in the function of the cardiovascular, respiratory and central nervous systems. Experimental results indicate that A1R can form a homodimer and that the protomer-protomer interaction in the A1R dimer is related to certain pharmacological characteristics of A1R activation. In this work, we performed docking, metadynamics simulation, conventional molecular dynamics simulations, Gaussian-accelerated molecular dynamics simulations, potential of mean force calculations, dynamic cross-correlation motions analysis and community network analysis to study the binding mode of 5'-N-ethylcarboxamidoadenosine (NECA) to A1R and the effect of dimerization on the activation of A1R. Our results show that NECA binds to A1R in a similar mode to adenosine in the A1R crystal structure and NECA in the A2AR crystal structure. The A1R homodimer can be activated by one or two agonists with NECA occupying its orthosteric pockets in one (which we call the NECA-A1R system) or both protomers (which we call the dNECA-A1R system). In the NECA-A1R system, activation is predicated in the protomer without NECA bound. In the dNECA-A1R system, only one protomer achieves the active state. These findings suggest an asymmetrical activation mechanism of the homodimer and a negative cooperativity between the two protomers. We envision that our results may further facilitate the drug development of A1R.


Assuntos
Dimerização , Modelos Moleculares , Receptor A1 de Adenosina/química , Receptor A1 de Adenosina/metabolismo , Cristalização , Humanos , Simulação de Dinâmica Molecular , Ligação Proteica , Estrutura Terciária de Proteína
3.
Adv Exp Med Biol ; 1172: 97-117, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31628653

RESUMO

The IL-17 family in humans consists of six distinct cytokines (IL-17A-F) that can interact with five IL-17 receptors (IL-17RA-E). The interaction between these cytokines and their receptors are critical in mediating host defenses while also making major contributions to inflammatory and autoimmune responses as demonstrated through both in vitro and in vivo experiments as well as human clinical trials. Inhibition of the IL-17A/IL-17RA interaction by monoclonal antibodies has also displayed remarkable efficacies in clinical trials against psoriasis and other autoimmune diseases. Recently, we and others reported the identification and characterization of both small-molecule and peptide IL-17A antagonists. These non-antibody IL-17A antagonists can effectively and selectively disrupt the IL-17A/IL-17RA complex and may provide alternative modalities to treat IL-17-related autoimmune and inflammatory diseases. This chapter summarizes the reported crystal structures of the IL-17 cytokines, their complexes with IL-17RA, and their complexes with both monoclonal antibodies as well as small-molecule and peptide antagonists.


Assuntos
Interleucina-17 , Receptores de Interleucina-17 , Animais , Anticorpos Monoclonais/química , Anticorpos Monoclonais/metabolismo , Doenças Autoimunes/imunologia , Cristalização , Humanos , Interleucina-17/antagonistas & inibidores , Interleucina-17/química , Interleucina-17/imunologia , Receptores de Interleucina-17/antagonistas & inibidores , Receptores de Interleucina-17/química , Receptores de Interleucina-17/imunologia
4.
Phys Chem Chem Phys ; 21(36): 19944-19950, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31475699

RESUMO

In this manuscript the ability of closo-carboranes to establish CHπ and BHπ interactions with several aromatic moieties exhibiting different electronic natures has been evaluated at the PBE0-D3/def2-TZVP level of theory. We have used the three closo isomers (ortho-, meta-, and para-) and benzene, trifluorobenzene and hexafluorobenzene as aromatic systems. Furthermore, we have used Bader's theory of "atoms in molecules" to further describe and characterize the noncovalent interactions described herein from a charge-density perspective. Finally, several biological examples retrieved from the PDB are also included, highlighting the impact of these interactions in the binding affinity of boron tracedrugs.


Assuntos
Compostos de Boro/química , Modelos Químicos , Cristalização , Tetra-Hidrofolato Desidrogenase/química , Tetra-Hidrofolato Desidrogenase/metabolismo , Vitamina D/química , Vitamina D/metabolismo , Raios X
5.
J Phys Chem Lett ; 10(20): 5997-6002, 2019 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-31545052

RESUMO

The classical method for evaluating the waveguide ability only focuses on the optical loss coefficient. However, for the micro- or submicroscale, an organic waveguide is demonstrated by the present study whose scale effect should not be neglected. We found that the optical loss coefficient increased remarkably when decreasing the sectional size of the microfibers. Furthermore, simulations based on Finite-Difference Time-Domain also demonstrated the size-dependent effect of the waveguide. Both the experimental and simulating results showed that the optical loss coefficient converges to a certain value, which means that the scale effect can be neglected as the sectional size is large enough. On the basis of the present study, we suggest that the scale-dependent effect on the sectional size of the waveguide should be investigated by evaluating the waveguide ability by the optical loss coefficient.


Assuntos
Cumarínicos/efeitos da radiação , ortoaminobenzoatos/efeitos da radiação , Cumarínicos/química , Cristalização , Fluorescência , Luz , Manufaturas/efeitos da radiação , Espectroscopia de Infravermelho com Transformada de Fourier , Eletricidade Estática , Difração de Raios X , ortoaminobenzoatos/química
6.
Chem Pharm Bull (Tokyo) ; 67(9): 915-920, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31474729

RESUMO

Controlling drug crystallization is one of the important issues in pre-formulation study. In recent years, advanced approaches including the use of tailor-made additives have gathered considerable attention to control crystallization behavior of drugs. This review focuses on the use of hydrophilic cyclodextrins (CDs) as additives for controlling drug crystallization. CDs affect the crystallization of drugs in solution and in solid state based on a host-guest interaction. For example, 2,6-di-O-methyl-ß-CD and 2-hydroxybutyl-ß-CD suppressed solution-mediated transition of drugs during crystallization by the host-guest interaction; as a result, metastable forms selectively precipitated in solution. The use of CDs in crystal engineering provided an opportunity for the detection of a new polymorph by changing the crystallization pathway. It was also possible to modify crystal morphology (i.e., crystal habit) by selective suppression of crystal growth on a certain direction based on the host-gust interaction. For solid formulation, stable amorphous drug/CDs complex under humid conditions was prepared using two different CDs. An overview of some recent progress in the use of CDs in crystal engineering and in amorphous formulation is described in this review.


Assuntos
Preparações Farmacêuticas/química , beta-Ciclodextrinas/química , Acetoexamida/química , Aspirina/química , Cristalização , Composição de Medicamentos , Interações Hidrofóbicas e Hidrofílicas
7.
Chem Pharm Bull (Tokyo) ; 67(9): 940-944, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31474733

RESUMO

The photostability of three types of furosemide (FUR) cocrystal (FUR-caffeine, FUR-urea, and FUR-nicotinamide cocrystals) was studied under irradiation with a D65 fluorescent lamp. The coloration of the FUR-urea pellets was significantly faster than that of the intact FUR, whereas the coloration of FUR-nicotinamide was suppressed compared with that of intact FUR and the other cocrystals. In the case of FUR-urea, the chemical degradation of FUR increased by approximately 6.6% after irradiation for 90 d. On the other hand, FUR-nicotinamide showed better chemical stability, with only 1.3% of FUR degraded, which was significantly lower than the other cocrystals. The FUR-urea pellets showed a UV-Visible absorption spectrum similar to that of intact FUR, while the absorption range of FUR-nicotinamide shifted to a shorter wavelength. The light sensitivity of FUR-nicotinamide was improved because of the much lower emission of the D65 fluorescent lamp in the absorption range of the cocrystal.


Assuntos
Cafeína/química , Furosemida/química , Luz , Niacinamida/química , Ureia/química , Cristalização , Estabilidade de Medicamentos , Espectrofotometria
8.
Chem Pharm Bull (Tokyo) ; 67(9): 945-952, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31474734

RESUMO

Salt and cocrystal formulations are widely used as techniques to improve physicochemical properties of compounds. Some spectrometric techniques to distinguish cocrystals from salts have been reported; however, it has not been possible to adapt these formulations with many compounds, because of limitations, high difficulty, and exceptions. Therefore, we focused on the possibility of UV spectrometry, which had not been reported as a classification technique for salts and cocrystals. The integration values of solid-state UV/visible (Vis) spectra of indomethacin salts were larger than those of physical mixtures of indomethacin and counter molecules, while that of indomethacin cocrystal was not large compared with that of the physical mixture. From these results, differences between a salt and a cocrystal were observed in their solid-state UV/Vis absorption spectra for indomethacin complexes. Therefore, it is suggested that solid-state UV/Vis absorption spectra can be used as a new technique to classify salts and cocrystals.


Assuntos
Indometacina/química , Espectrofotometria Ultravioleta/métodos , Arginina/química , Cristalização , Espectroscopia de Ressonância Magnética , Meglumina/química , Sacarina/química , Sais/química , Difração de Raios X
9.
Pharm Res ; 36(10): 150, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31428879

RESUMO

PURPOSE: The unconventional tabletability of the indomethacin polymorphs - α and γ - are investigated from a topological and mechanical perspective using powder Brillouin light scattering (p-BLS) to identify the specific structure-performance relationship in these materials. METHOD: Indomethacin (γ-form) was purchased and used to prepare the α polymorph. Powder X-ray diffraction was used to confirm phase identity, while p-BLS was used to obtain the mechanical properties. Energy frameworks were determined with Crystal Explorer to visualize the interaction topologies. Using a Carver press and a stress-strain analyzer, the tableting performance of each polymorph was determined. RESULTS: Polymorph-specific acoustic frequency distributions were observed with distinct, zero-porosity, aggregate elastic moduli determined. The p-BLS spectra for α-indomethacin display a population of low-velocity shear modes, indicating a direction of facilitated shear. This improves slip-mediated plasticity and tabletability. Our p-BLS spectra experimentally indicates that a low-energy slip system is available to α-indomethacin which supports ours and previous energy framework calculations. Despite a 2d-layered crystal motif favorable for shear deformation, the γ-form displays a higher shear modulus that is supported by our hydrogen-bonding analysis of γ-indomethacin. CONCLUSION: Our experimental, mechanical data is consistent with the predicted interaction topologies and these two inputs combined permit a comprehensive, molecular understanding of polymorph-specific tabletability.


Assuntos
Indometacina/química , Cristalização , Dimerização , Composição de Medicamentos , Ligações de Hidrogênio , Luz , Fenômenos Mecânicos , Porosidade , Pós , Espalhamento de Radiação , Comprimidos , Termodinâmica
10.
Chem Pharm Bull (Tokyo) ; 67(8): 816-823, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31366831

RESUMO

In this present study a new co-crystals of zoledronic acid with DL-tartaric acid and nicotinamide has been developed with improved solubility. Zoledronic acid is a class III drug with poor oral bioavailability due to its poor permeability and low aqueous solubility; hence an attempt has been made to improve its solubility by co-crystallization technology. Pharmaceutical cocrystals are multi-component crystals with a stoichiometric ratio of active pharmaceutical ingredients (APIs) and cocrystal coformers (CCFs) that are assembled by noncovalent interactions such as hydrogen bonds, π-π packing, and Vander Waals forces. In this study the coformers selected were DL-tartaric acid and nicotinamide based on ease of hydrogen bond formation. The co-crystal of zoledronic acid with DL-tartaric acid were prepared in three ratios (1 : 1, 1 : 2 and 2 : 1) by slow solvent evaporation method and with nicotinamide in 1 : 1 ratio by dry grinding method. The formation of co-crystal was confirmed by powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC) and Fourier transform (FT)IR. The dynamic solubility of co-crystals with DL-tartaric acid in the ratios 1 : 1, 1 : 2 and 2 : 1 increased by fold as compared to pure drug.


Assuntos
Desenho de Drogas , Niacinamida/química , Tartaratos/química , Ácido Zoledrônico/química , Varredura Diferencial de Calorimetria , Cristalização , Estrutura Molecular , Difração de Pó , Solubilidade , Ácido Zoledrônico/síntese química
11.
Vasc Health Risk Manag ; 15: 209-220, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31371977

RESUMO

Cholesterol-embolization syndrome (CES) is a multisystemic disease with various clinical manifestations. CES is caused by embolization of cholesterol crystals (CCs) from atherosclerotic plaques located in the major arteries, and is induced mostly iatrogenically by interventional and surgical procedures; however, it may also occur spontaneously. Embolized CCs lead to both ischemic and inflammatory damage to the target organ. Therefore, anti-inflammatory agents, such as corticosteroids and cyclophosphamide, have been investigated as treatment for CES in several studies, with conflicting results. Recent research has revealed that CES is actually a kind of autoinflammatory disease in which inflammasome pathways, such as NLRP3 and IL1, are induced by CCs. These recent findings may have clinical implications such that colchicine and IL1 inhibitors, namely canakinumab, may be beneficial in the early stages of CES.


Assuntos
Aterosclerose , Colesterol/sangue , Embolia de Colesterol , Corticosteroides/uso terapêutico , Animais , Anti-Inflamatórios/uso terapêutico , Aterosclerose/sangue , Aterosclerose/diagnóstico , Aterosclerose/tratamento farmacológico , Aterosclerose/epidemiologia , Biomarcadores/sangue , Cristalização , Embolia de Colesterol/sangue , Embolia de Colesterol/diagnóstico , Embolia de Colesterol/epidemiologia , Embolia de Colesterol/prevenção & controle , Humanos , Imunossupressores/uso terapêutico , Inflamassomos/sangue , Mediadores da Inflamação/sangue , Interleucina-1/sangue , Proteína 3 que Contém Domínio de Pirina da Família NLR/sangue , Placa Aterosclerótica , Prognóstico , Fatores de Risco , Síndrome
12.
N Engl J Med ; 381(9): 882-884, 2019 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-31461600
13.
Phys Chem Chem Phys ; 21(34): 18501-18515, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31411212

RESUMO

Cohesive properties (lattice and cohesive energy of the crystal and corresponding sublimation enthalpy) of the complete set of twenty enantiopure anhydrous proteinogenic amino acids are investigated using first-principles calculations. In contrast to neutral amino acid molecules in the vapor phase, all amino acids form crystals in their zwitterionic form. Therefore, reliable ab initio calculations of the proton transfer energy are an indispensable step of such calculations. Simplifying procedures, designed to rationalize the computational cost of the quasi-harmonic approximation, which proves too demanding if performed fully at the given quantum level of theory, are presented and tested. For this purpose, atomic multipoles (up to the quadrupoles) for the amoeba force field are parametrized for all amino acid zwitterions. While the calculated lattice energies of the amino acids range from 235-458 kJ mol-1 in absolute value, the proton transfer energies typically amount to 100-220 kJ mol-1, which translates to sublimation enthalpies ranging from 117-202 kJ mol-1, appreciably exceeding the sublimation enthalpy values common for nonionic molecular crystals. Critically assessed experimental data on sublimation enthalpies are used as a benchmark for comparison of the data calculated in this work. Cohesive properties of most amino acids calculated in this work, combining the PBE-D3(BJ)/PAW and CCSD(T)-F12/aug-cc-pVDZ levels of theory used for predictions of the lattice energies and of the proton transfer energies, respectively, exhibit a reasonable agreement with the experiment. At the same time, this work contains the first published data on cohesive properties for several enantiopure amino acids.


Assuntos
Aminoácidos/química , Simulação por Computador , Cristalização , Transição de Fase , Prótons , Teoria Quântica , Termodinâmica
14.
Phys Chem Chem Phys ; 21(35): 19192-19200, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31436279

RESUMO

Despite advances, tuberculosis remains a significant infectious disease, whose mortality presents alarming numbers. Although it can be cured, the number of cases of antimicrobial resistant strains is increasing, requiring the use of less efficient second-line drugs. Capreomycin and streptomycin are part of this group, being antibiotics whose mechanism of action is the inhibition of protein synthesis when interacting with the tuberculosis bacterial ribosome. Their binding mechanisms are distinct: capreomycin is able to bind to both ribosomal (30S and 50S) subunits, whereas streptomycin binds only to the smaller one (30S). In this context, the biochemical characterization of these binding sites for a proper understanding of their complex interactions is of crucial importance to increase their efficacy. Through crystallographic data and computer simulations, in this work we calculated the interaction binding energies of capreomycin and streptomycin in complex with the tuberculosis bacterial ribosome subunits, by using density functional theory (DFT) within the molecular fractionation with conjugated caps (MFCC) approach. For capreomycin in the 30S (50S) subunit, we investigated the binding energies of 44 (30) residues presented within a pocket radius of 14 Å (30 Å). Regarding streptomycin, 60 nucleotide (25 amino acid) residues distributed up to 12.5 Å (15 Å) away from the drug in the 30S subunit (S12 protein) were taken into account. We also identify the contributions of hydrogen bonds and hydrophobic interactions in the drug-receptor complex, and the regions of the drugs that most contributed to the anchorages of them in their binding sites, as well as identify residues that are most associated with mutations.


Assuntos
Antibacterianos/química , Capreomicina/química , Metabolismo Energético , Mycobacterium tuberculosis/metabolismo , Subunidades Ribossômicas/química , Subunidades Ribossômicas/metabolismo , Estreptomicina/química , Antibacterianos/metabolismo , Antibacterianos/uso terapêutico , Capreomicina/metabolismo , Capreomicina/uso terapêutico , Simulação por Computador , Cristalização , Humanos , Mutação , Mycobacterium tuberculosis/química , Receptores de Droga/genética , Receptores de Droga/metabolismo , Estreptomicina/metabolismo , Estreptomicina/uso terapêutico , Tuberculose/tratamento farmacológico , Tuberculose/microbiologia
15.
AAPS PharmSciTech ; 20(7): 273, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31385126

RESUMO

Orodispersible films (ODFs) are more convenient for paediatric and geriatric patients to take as compared to conventional tablets and capsules. Electrospinning has recently been attempted to produce ODFs. This study investigated the feasibility of formulating poorly water-soluble drug into ODFs using electrospinning technology coupled with the anti-solvent precipitation method. Piroxicam (PX), a poorly water-soluble drug, was chosen as a model drug. Polyvinyl alcohol and polyvinylpyrrolidone were used as film forming polymers. PX microcrystals were prepared using poloxamer as the stabilizer with the anti-solvent precipitation method, and then loaded in ODFs through the electrospinning process. The obtained ODFs were characterized using a scanning electron microscope, X-ray powder diffraction and Fourier transform infrared spectroscopy with respect to the morphology, solid state and potential molecular interaction between the model drug and polymers. The mechanical property, disintegration and dissolution rate of the obtained ODF were evaluated using dynamic mechanical analysis, a customized method and USP2 apparatus. The results showed that PX microcrystals suspended in polymeric solutions could be readily electrospun into fibrous films, where the microcrystals scattered between the fibers. The electrospun fibrous film-based ODFs exhibited satisfactory mechanical behaviour, and fast disintegration upon the polymer selection. In the dissolution tests, almost 90% of PX was dissolved within 6 min from the ODFs, whereas 40% of PX dissolved from physical mixtures in 60 min. This study demonstrated that poorly water-soluble drugs could be formulated into ODFs with satisfactory quality attributes by combining micronization and the electrospinning process.


Assuntos
Anti-Inflamatórios não Esteroides/síntese química , Química Farmacêutica/métodos , Portadores de Fármacos/síntese química , Piroxicam/síntese química , Água/química , Administração Oral , Cristalização , Humanos , Polímeros/química , Álcool de Polivinil/química , Solubilidade , Solventes/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Comprimidos , Difração de Raios X/métodos
16.
Food Chem ; 298: 125015, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260956

RESUMO

The effect of microwave irradiation-retrogradation (MIR) treatment on the physicochemical properties and in vitro digestibility of corn starch (A-type crystallinity), potato starch (B-type) and chestnut starch (C-type) were evaluated. After MIR treatment, the amount of resistant starch (RS) increased and rapid digestible starch (RDS) decreased along with the retrogradation time in all three starches. The degree of retrogradation (DR) of starch was significantly positive correlated with amylose and RS content. All three starches subjected to MIR treatment exhibited a B-type crystalline structure. With the increase in retrogradation time, starch granules became more orderly. The DR was significantly positively correlated with relative crystallinity of X-ray pattern, To, ΔH of thermal properties, and the Fourier transform infrared ratio of 1047/1022 cm-1 of starch. The results indicated that MIR treatment is a good industrial method for preparing low digestive starch and retrogradation time is an important parameter for the process.


Assuntos
Amilose/efeitos da radiação , Amido/efeitos da radiação , Amilose/química , Fenômenos Químicos/efeitos da radiação , Cristalização , Micro-Ondas , Espectroscopia de Infravermelho com Transformada de Fourier , Amido/química , Difração de Raios X
17.
Bioresour Technol ; 290: 121779, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31310868

RESUMO

Based on the requirements for advanced treatment and resource recovery of nitrogen and phosphorus pollutants in wastewater, the coupled anammox and hydroxyapatite crystallization (anammox-HAP) process was studied with an aim of achieving high efficiency and low energy consumption during simultaneous nitrogen and phosphorus removal. In the long-term experiments and batch tests, the effects of substrate conditions (nitrogen and phosphorus load, calcium concentration, etc.) on the nitrogen removal and phosphorus recovery efficiencies were investigated. The granular structure and crystal properties were analyzed together with microscopic characterization methods, and the formation mechanism of coupled anammox-HAP granules was verified. Based on these experiments, a theoretical model and technical method for realizing the coupled process were established, and a reference for practical engineering application was provided.


Assuntos
Nitrogênio , Fósforo , Reatores Biológicos , Cristalização , Desnitrificação , Durapatita , Oxirredução
18.
Phys Chem Chem Phys ; 21(31): 17142-17151, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31339149

RESUMO

In this work we compute high-coverage hydrogen adsorption energies and geometries on the stepped platinum surfaces Pt(211) and Pt(533) which contain a (100)-step type and the Pt(221) and Pt(553) surface with a (111) step edge. We discuss these results in relation to ultra-high-vacuum temperature programmed desorption (TPD) data to elucidate the origin of the desorption features. Our results indicated that on surfaces with a (100)-step type, two distinct ranges of adsorption energy for the step and terrace are observed, which mirrors the TPD spectra for which we find a clear separation of the desorption peaks. For the (111) step type, the TPD spectra show much less separation of the step and terrace features, which we assign to the low individual adsorption energies for H atoms on this step edge. From our results we obtain a much clearer understanding of the surface-hydrogen bonding at high coverages and the origin of the different TPD features present for the two step types studied.


Assuntos
Teoria da Densidade Funcional , Hidrogênio/química , Platina/química , Adsorção , Cristalização , Ligações de Hidrogênio , Temperatura Ambiente , Termodinâmica
19.
J Environ Manage ; 248: 109254, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31306927

RESUMO

Phosphorus is an essential element for life and is predicted to deplete within the next 100 years. Struvite crystallization is a potential phosphorus recovery technique to mitigate this problem by producing a slow release fertilizer. However, complex wastewater composition and a large number of process variables result in process uncertainties, making the process difficult to predict and control. This paper reviews the research progress on struvite crystallization fundamentals to address this challenge. The influence of manipulated variables (e.g. seed material, magnesium dosage and pH) and sources of variation on phosphorus removal efficiency (e.g. organics and heavy metal concentration) and product purity were investigated. Recently developed models to describe, control and optimize those variables were also discussed. This review helps to identify potential challenges in different wastewater streams and provide valuable information for future phosphorus recovery unit design. It therefore paves the way for commercialization of struvite crystallization in the future.


Assuntos
Fósforo , Águas Residuárias , Cristalização , Compostos de Magnésio , Fosfatos , Estruvita
20.
J Phys Chem Lett ; 10(15): 4278-4284, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31318218

RESUMO

Silk continues to amaze: over the past decade, new research threads have emerged that include the use of silk fibroin for advanced pharmaceutics, including its suitability for drug delivery. Despite this ongoing interest, the details of silk fibroin structures and their subsequent drug interactions at the molecular level remain elusive, primarily because of the difficulties encountered in modeling the silk fibroin molecule. Here, we generated an atomistic silk model containing amorphous and crystalline regions. We then exploited advanced well-tempered metadynamics simulations to generate molecular conformations that we subsequently exposed to classical molecular dynamics simulations to monitor both drug binding and release. Overall, this study demonstrated the importance of the silk fibroin primary sequence, electrostatic interactions, hydrogen bonding, and higher-order conformation in the processes of drug binding and release.


Assuntos
Doxorrubicina/química , Portadores de Fármacos/química , Fibroínas/química , Animais , Bombyx/química , Cristalização , Liberação Controlada de Fármacos , Ligações de Hidrogênio , Simulação de Dinâmica Molecular , Conformação Proteica , Eletricidade Estática , Termodinâmica , Água/química
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