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1.
J Vis Exp ; (186)2022 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-36063015

RESUMO

An accurate mechanistic description of water crystallization is challenging and requires a few key elements: superb temperature control to allow the formation of single microscopic crystals and a suitable microscopy system coupled to the cold stage. The method described herein adds another important feature that includes exchanging solutions around ice and clathrate hydrate crystals. The described system comprises a combination of unique and home-developed instruments, including microfluidics, high-resolution cold stages, and fluorescence microscopy. The cold stage was designed for microfluidic devices and allows for the formation of micron-sized ice/hydrate crystals inside microfluidic channels and the exchange of solutions around them. The temperature resolution and stability of the cold stage is one millikelvin, which is crucial for controlling the growth of these small crystals. This diverse system is used to study the different processes of ice and hydrate crystallization and the mechanism by which the growth of these crystals is inhibited. The protocol describes how to prepare microfluidic devices, how to grow and control microscopic crystals in the microfluidic channels, and how the utilization of the flow of liquids around ice/hydrate crystals affords new insights into the crystallization of water.


Assuntos
Gelo , Microfluídica , Cristalização , Temperatura , Água/química
2.
Biochem Biophys Res Commun ; 628: 98-103, 2022 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-36084557

RESUMO

A cryoprotectant known as ice-binding protein (IBP) is thought to facilitate the cold survival of plants, insects, and fungi. Here, we prepared a genetically modified Caenorhabditis elegans strain to synthesize fish-derived IBPs in its body wall muscles and examined whether the antifreeze activity modification of this IBP by point mutation affects the cold tolerance of this worm. We chose a 65-residue IBP identified from notched-fin eelpout, for which the replacement of the 20th alanine residue (A20) modifies its antifreeze activity. These mutant proteins are denoted A20L, A20G, A20T, A20V, and A20I along with the wild-type (WT) protein. We evaluated the survival rate (%) of the transgenic C. elegans that synthesized each IBP mutant following 24 h of preservation at -5, +2, and +5 °C. Significantly, a dramatic improvement in the survival rate was detected for the worms synthesizing the activity-enhanced mutants (A20T and A20I), especially at +2 °C. In contrast, the rate was not improved by the expression of the defective mutants (A20L, A20G, WT and A20V). The survival rate (%) probably correlates with the antifreeze activity of the IBP. These data suggest that IBP protects the cell membrane by employing its ice-binding mechanism, which ultimately improves the cold tolerance of an IBP-containing animal.


Assuntos
Proteínas Anticongelantes , Gelo , Alanina/genética , Animais , Proteínas Anticongelantes/química , Proteínas Anticongelantes/genética , Proteínas Anticongelantes/metabolismo , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Transporte/metabolismo , Proteínas de Peixes/genética , Congelamento , Proteínas Mutantes/metabolismo , Mutação , Compostos Organotiofosforados
3.
J Food Sci ; 87(9): 4082-4106, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-36049017

RESUMO

A hybrid mixture theory (HMT)-based unsaturated transport (pores not saturated with liquid) model was applied to a food matrix subjected to freezing and freeze-thaw cycles. The model can explain the fluid, species, and heat transport, ice formation, thermomechanical changes, and the freezing point depression occurring inside food biopolymers during freezing. Volume changes during freezing were calculated using the stresses due to pore pressure and the phase-change based mechanical strain. The Eulerian-Lagrangian transformation was performed for solving the equations using a finite element mesh in Lagrangian coordinates. The predicted temperature profiles for constant and fluctuating freezing temperature conditions showed agreement with experimental data with reasonable accuracy (RMSE = 2.86°C and 2.23°C, respectively). The multiscale transport model coupled with a physical chemistry-based relation was able to predict solute concentration and the freezing point depression in potatoes with greater accuracy than an empirical equation published in the literature. Sudden temperature fluctuations representing the opening and closing of a freezer door were investigated using this solution scheme, and conditions causing less damage to the food were identified. PRACTICAL APPLICATION: Food materials are subjected to freeze-thaw cycles during storage, shipping, and distribution to the consumers. The study uses numerical modeling and experimental validation to elucidate the principles affecting ice formation, solute migration, and temperature changes. Outcomes will allow processors to improve the quality of frozen foods with improved design of freezing operation, and storage and distribution strategies.


Assuntos
Temperatura Alta , Gelo , Biopolímeros , Congelamento , Alimentos Congelados
4.
Langmuir ; 38(37): 11346-11353, 2022 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-36066243

RESUMO

Ice affects many chemical reactions in nature, which greatly influences the atmosphere, climate, and life. However, the exact mechanism of ice in these chemical reactions remains elusive. For example, it is still an open question as to whether ice can act as a catalyst to greatly enhance the reactivity and selectivity, which is essential for the production of some natural compounds in our planet. Here, we discover that ice can lead to high efficiency and stereoselectivity of the [2 + 2] photodimerization of coumarin and its derivatives. The conversion of the [2 + 2] photodimerization of coumarins enhanced by ice is dozens of times higher than that in the unfrozen saturated solution, and the reaction displays a high syn-head-head stereoselectivity (>95%) in comparison with those in the absence of the ice. Note that almost no reaction occurs in the crystal powder and melt of the coumarins, indicating that the role of ice in the photodimerization reaction is not simply due to the usual mechanisms found in the freezing concentration. We further reveal that the reaction rate is found to be proportional to the total area of the ice surface and follows Michaelis-Menten-like kinetics, indicating that the ice surface catalyzes the reaction. Molecular dynamics simulations demonstrate that ice surfaces can induce reactants to form a two-dimensional liquid-crystal-ordered layer with a suitable intermolecular distance and unique side-by-side packing, facilitating stereoselective photodimerization for syn-head-head dimers. These findings give evidence that ice-surface-induced molecular assembly may play an important role in atmospheric heterogeneous photoreaction processes.


Assuntos
Cumarínicos , Gelo , Cumarínicos/química , Congelamento , Gelo/análise , Cinética , Pós
5.
PLoS One ; 17(9): e0274034, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36103476

RESUMO

Mutations of the nucleophosmin1 (NPM1) gene represent the most frequent molecular alteration in acute myelogenous leukemia (AML), especially in patients with AML who have a normal karyotype. These alterations have been shown to carry favorable prognostic significance in patients with AML. Several methods have been developed for detection of NPM1 gene mutations. However, their ability to detect low levels of mutations in a wild-type background is limited. In this study, the Enhance improved and complete enrichment Co-amplification at Lower Denaturation temperature Polymerase Chain Reaction (E-ice-COLD-PCR) assay combined with High Resolution Melting (HRM) analysis was developed and validated for highly specific and sensitive screening for NPM1 gene mutations. A total of 83 blood samples from patients with AML were collected, and their DNA was extracted. For mutational analysis, the E-ice-COLD-PCR assay for the detection of NPM1 gene mutations was developed. PCR products were analyzed by HRM analysis. All positive samples were confirmed by direct sequencing. This assay enabled detection specificity and sensitivity of NPM1 mutations in 9/83 patients with AML. Direct sequencing results were 100% concordant with this method. In addition, the limit of detection was 12.5% mutant in the final concentration of 5 ng genomic DNA. The E-ice-COLD-PCR assay with HRM analysis is a highly specific and sensitive screening method for enrichment of detecting NPM1 gene mutations. This method has both a short turn around time and easier interpretation compared to those of other methods.


Assuntos
Gelo , Leucemia Mieloide Aguda , Humanos , Leucemia Mieloide Aguda/diagnóstico , Leucemia Mieloide Aguda/genética , Mutação , Proteínas Nucleares/genética , Reação em Cadeia da Polimerase/métodos
6.
Nat Commun ; 13(1): 5156, 2022 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-36056046

RESUMO

How lake temperatures across large geographic regions are responding to widespread alterations in ice phenology (i.e., the timing of seasonal ice formation and loss) remains unclear. Here, we analyse satellite data and global-scale simulations to investigate the contribution of long-term variations in the seasonality of lake ice to surface water temperature trends across the Northern Hemisphere. Our analysis suggests a widespread excess lake surface warming during the months of ice-off which is, on average, 1.4 times that calculated during the open-water season. This excess warming is influenced predominantly by an 8-day advancement in the average timing of ice break-up from 1979 to 2020. Until the permanent loss of lake ice in the future, excess lake warming may be further amplified due to projected future alterations in lake ice phenology. Excess lake warming will likely alter within-lake physical and biogeochemical processes with numerous implications for lake ecosystems.


Assuntos
Gelo , Lagos , Ecossistema , Estações do Ano , Temperatura , Água
7.
Sci Rep ; 12(1): 15330, 2022 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-36097274

RESUMO

While recent technological developments contributed to breakthrough advances in single particle cryo-electron microscopy (cryo-EM), sample preparation remains a significant bottleneck for the structure determination of macromolecular complexes. A critical time factor is sample optimization that requires the use of an electron microscope to screen grids prepared under different conditions to achieve the ideal vitreous ice thickness containing the particles. Evaluating sample quality requires access to cryo-electron microscopes and a strong expertise in EM. To facilitate and accelerate the selection procedure of probes suitable for high-resolution cryo-EM, we devised a method to assess the vitreous ice layer thickness of sample coated grids. The experimental setup comprises an optical interferometric microscope equipped with a cryogenic stage and image analysis software based on artificial neural networks (ANN) for an unbiased sample selection. We present and validate this approach for different protein complexes and grid types, and demonstrate its performance for the assessment of ice quality. This technique is moderate in cost and can be easily performed on a laboratory bench. We expect that its throughput and its versatility will contribute to facilitate the sample optimization process for structural biologists.


Assuntos
Gelo , Interferometria , Microscopia Crioeletrônica/métodos , Substâncias Macromoleculares/química , Manejo de Espécimes/métodos
8.
Nat Commun ; 13(1): 4974, 2022 08 25.
Artigo em Inglês | MEDLINE | ID: mdl-36008420

RESUMO

The quality of lake ice is of uppermost importance for ice safety and under-ice ecology, but its temporal and spatial variability is largely unknown. Here we conducted a coordinated lake ice quality sampling campaign across the Northern Hemisphere during one of the warmest winters since 1880 and show that lake ice during 2020/2021 commonly consisted of unstable white ice, at times contributing up to 100% to the total ice thickness. We observed that white ice increased over the winter season, becoming thickest and constituting the largest proportion of the ice layer towards the end of the ice cover season when fatal winter drownings occur most often and light limits the growth and reproduction of primary producers. We attribute the dominance of white ice before ice-off to air temperatures varying around the freezing point, a condition which occurs more frequently during warmer winters. Thus, under continued global warming, the prevalence of white ice is likely to substantially increase during the critical period before ice-off, for which we adjusted commonly used equations for human ice safety and light transmittance through ice.


Assuntos
Gelo , Lagos , Aquecimento Global , Humanos , Camada de Gelo , Estações do Ano , Temperatura
9.
Quintessence Int ; 53(9): 772-777, 2022 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-35976753

RESUMO

OBJECTIVES: To evaluate the effect of kinesiology tape application after mandibular third molar extraction. METHOD AND MATERIALS: Patients with mandibular third molar extraction indications were divided into three groups. The patients in group 1 had kinesiology tape applied after tooth extraction, the patients in group 2 were given an ice pack and intermittent cryotherapy within 24 h of the operation, and the patients in group 3 were not given any additional intervention. All patients were followed up, and the postoperative swelling, pain, mouth opening limitation, and quality of life were recorded and evaluated. Comments on the intervention methods from patients were also collected. RESULTS: Compared to group 3, groups 1 and 2 showed a significant reduction in postoperative swelling, pain, and limitation of mouth opening, and improvement of quality of life. There was no significant difference between groups 1 and 2 in each index, but the patients in group 1 reported fewer problems than those in group 2. CONCLUSIONS: The application of kinesiology tape was helpful in reducing the postoperative inflammatory symptoms of mandibular third molar extraction and improved the patients' postoperative quality of life. These results suggest that kinesiology tape can be used as an auxiliary treatment to cryotherapy or as an alternative intervention after mandibular third molar extraction.


Assuntos
Dente Serotino , Dente Impactado , Crioterapia/métodos , Edema , Humanos , Gelo , Mandíbula/cirurgia , Dente Serotino/cirurgia , Dor Pós-Operatória , Qualidade de Vida , Extração Dentária/métodos , Dente Impactado/cirurgia , Trismo
10.
J Vis Exp ; (185)2022 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-35938795

RESUMO

Interest in liquid-electron microscopy (liquid-EM) has skyrocketed in recent years as scientists can now observe real-time processes at the nanoscale. It is extremely desirable to pair high-resolution cryo-EM information with dynamic observations as many events occur at rapid timescales - in the millisecond range or faster. Improved knowledge of flexible structures can also assist in the design of novel reagents to combat emerging pathogens, such as SARS-CoV-2. More importantly, viewing biological materials in a fluid environment provides a unique glimpse of their performance in the human body. Presented here are newly developed methods to investigate the nanoscale properties of virus assemblies in liquid and vitreous ice. To accomplish this goal, well-defined samples were used as model systems. Side-by-side comparisons of sample preparation methods and representative structural information are presented. Sub-nanometer features are shown for structures resolved in the range of ~3.5-Å-10 Å. Other recent results that support this complementary framework include dynamic insights of vaccine candidates and antibody-based therapies imaged in liquid. Overall, these correlative applications advance our ability to visualize molecular dynamics, providing a unique context for their use in human health and disease.


Assuntos
COVID-19 , Gelo , Microscopia Crioeletrônica/métodos , Humanos , SARS-CoV-2 , Manejo de Espécimes
11.
Int J Mol Sci ; 23(15)2022 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-35955596

RESUMO

The cryopreservation of red blood cells (RBCs) plays a key role in blood transfusion therapy. Traditional cryoprotectants (CPAs) are mostly organic solvents and may cause side effects to RBCs, such as hemolysis and membrane damage. Therefore, it is necessary to find CPAs with a better performance and lower toxicity. Herein, we report for the first time that N-[Tri(hydroxymethyl)methyl]glycine (tricine) showed a great potential in the cryopreservation of sheep RBCs. The addition of tricine significantly increased the thawed RBCs' recovery from 19.5 ± 1.8% to 81.2 ± 8.5%. The properties of thawed RBCs were also maintained normally. Through mathematical modeling analysis, tricine showed a great efficiency in cryopreservation. We found that tricine had a good osmotic regulation capacity, which could mitigate the dehydration of RBCs during cryopreservation. In addition, tricine inhibited ice recrystallization, thereby decreasing the mechanical damage from ice. Tricine could also reduce oxidative damage during freezing and thawing by scavenging reactive oxygen species (ROS) and maintaining the activities of endogenous antioxidant enzymes. This work is expected to open up a new path for the study of novel CPAs and promote the development of cryopreservation of RBCs.


Assuntos
Antioxidantes , Gelo , Animais , Antioxidantes/farmacologia , Criopreservação , Crioprotetores/química , Crioprotetores/farmacologia , Eritrócitos , Glicina/análogos & derivados , Glicina/farmacologia , Ovinos
12.
Commun Biol ; 5(1): 817, 2022 08 15.
Artigo em Inglês | MEDLINE | ID: mdl-35965271

RESUMO

Ice thickness is arguably one of the most important factors limiting the resolution of protein structures determined by cryo-electron microscopy (cryo-EM). The amorphous atomic structure of the ice that stabilizes and protects biological samples in cryo-EM grids also imprints some additional noise in cryo-EM images. Ice that is too thick jeopardizes the success of particle picking and reconstruction of the biomolecule in the worst case and, at best, deteriorates eventual map resolution. Minimizing the thickness of the ice layer and thus the magnitude of its noise contribution is thus imperative in cryo-EM grid preparation. In this paper we introduce MeasureIce, a simple, easy to use ice thickness measurement tool for screening and selecting acquisition areas of cryo-EM grids. We show that it is possible to simulate thickness-image intensity look-up tables, also usable in SerialEM and Leginon, using elementary scattering physics and thereby adapt the tool to any microscope without time consuming experimental calibration. We benchmark our approach using two alternative techniques: the "ice channel" technique and tilt-series tomography. We also demonstrate the utility of ice thickness measurement for selecting holes in gold grids containing an Equine apoferritin sample, achieving a 1.88 Ångstrom resolution in subsequent refinement of the atomic map.


Assuntos
Microscopia Crioeletrônica/normas , Gelo , Proteínas/ultraestrutura , Animais , Apoferritinas/química , Apoferritinas/ultraestrutura , Benchmarking , Microscopia Crioeletrônica/métodos , Cavalos , Gelo/normas , Proteínas/química , Tomografia/métodos
14.
Biomed Mater ; 17(6)2022 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-36044885

RESUMO

Nanoconfinement within flexible interfaces is a key step towards exploiting confinement effects in several biological and technological systems wherein flexible 2D materials are frequently utilized but are arduous to prepare. Hitherto unreported, the synthesis of 2D hydrogel nanosheets (HNSs) using a template- and catalyst-free process is developed representing a fertile ground for fundamental structure-property investigations. In due course of time, nucleating folds propagating along the edges trigger co-operative deformations of HNS generating regions of nanoconfinement within trapped water islands. These severely constricting surfaces force water molecules to pack within the nanoscale regime of HNS almost parallel to the surface bringing about phase transition into puckered rhombic ice with AA and AB Bernal stacking pattern, which was mostly restricted to molecular dynamics studies so far. Interestingly, under high lateral pressure and spatial inhomogeneity within nanoscale confinement, bilayer rhombic ice structures were formed with an in-plane lattice spacing of 0.31 nm. In this work, a systematic exploration of rhombic ice formation within HNS has been delineated using high-resolution transmission electron microscopy, and its ultrathin morphology was examined using atomic force microscopy. Scanning electron microscopy images revealed high porosity while mechanical testing presented young's modulus of 155 kPa with ∼84% deformation, whereas contact angle suggested high hydrophilicity. The combinations of nanosheets, porosity, nanoconfinement, hydrophilicity, and mechanical strength, motivated us to explore their application as a scaffold for cartilage regeneration, by inducing chondrogenesis of human Wharton Jelly derived mesenchymal stem cells. HNS promoted the formation of cell aggregates giving higher number of spheroid formation and a marked expression of chondrogenic markers (ColI, ColII, ColX, ACAN and S-100), thereby providing some cues for guiding chondrogenic differentiation.


Assuntos
Células-Tronco Mesenquimais , Geleia de Wharton , Diferenciação Celular , Células Cultivadas , Condrogênese , Humanos , Hidrogéis/química , Gelo
15.
Astrobiology ; 22(9): 1047-1060, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-35972349

RESUMO

Landed missions to icy worlds with a subsurface liquid water ocean must meet planetary protection requirements and ensure a sufficiently small likelihood of any microorganism-bearing part of the landed element reaching the ocean. A higher bound on this likelihood is set by the potential for radioisotope thermoelectric generator (RTG) power sources, the hottest possible landed element, to melt through the ice shell and reach the ocean. In this study, we quantify this potential as a function of three key parameters: surface temperature, ice shell thickness (i.e., heat flux through the shell), and thickness of a porous (insulating) snow or regolith cover. Although the model we describe can be applied to any ocean world, we present results in the context of a landed mission concept to the south polar terrain of Saturn's moon Enceladus. In this particular context, we discuss planetary protection considerations for landing site selection. The likelihood of forward microbial contamination of Enceladus' ocean by an RTG-powered landed mission can be made sufficiently low to not undermine compliance with the planetary protection policy.


Assuntos
Meio Ambiente Extraterreno , Gelo , Oceanos e Mares , Planetas , Radioisótopos
16.
J Mater Chem B ; 10(36): 6922-6927, 2022 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-35979758

RESUMO

Cyclodextrin-based cryoprotectants were developed. α-TMCD, which can be easily put into large-scale production, showed enhanced cell viabilities of 19.97 ± 0.78%, 13.93 ± 4.46% and 19.10 ± 0.95% against GES-1, hucMSCs and A549 cells. Moreover, the viable cells observed by light microscope imaging showed that the enhanced hucMSC cell number percentage of α-TMCD was 103.2%. An α-TMCD-DMSO-based CPA exhibited an enhanced cryoprotective effect by a mechanism of DMSO-enhanced cell penetrating effect and α-TMCD-DMSO synergistically enhanced IMA ability. α-TMCD exhibited potential for the discovery of macrocycle-molecule-based cryoprotectants.


Assuntos
Crioprotetores , Ciclodextrinas , Amidas , Criopreservação/métodos , Crioprotetores/química , Crioprotetores/farmacologia , Ciclopropanos , Dimetil Sulfóxido , Gelo
17.
Ultramicroscopy ; 241: 113600, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-35988477

RESUMO

Muscle samples are commonly chemically fixed or frozen immediately upon collection for biochemical and morphological analysis. Certain fixatives such as glutaraldehyde and osmium tetroxide are widely used for transmission electron microscopy (TEM) and lead to adequate preservation of muscle ultrastructure, but do not preserve the molecular features of samples. Methacarn is suggested to be a preferable chemical fixative for light microscopy because it maintains immunohistological features of samples. However, the efficacy of methacarn to preserve ultrastructural features as a primary chemical fixative for TEM is currently unclear. Additionally, cryo-preservation of samples for TEM analysis involves freezing processes such as plunge freezing, slam freezing, or high pressure freezing. High pressure freezing is the considered the gold standard but requires costly equipment and may not be a viable option for many labs collecting tissue samples from remote locations. Dimethyl sulfoxide (DMSO) is a commonly used cryoprotectant that may allow for better structural preservation of samples by impairing ice damage that occurs during plunge/snap freezing. We aimed to assess the effectiveness of methacarn as a primary chemical fixative and determine the effect of pre-coating samples with DMSO before plunge/snap freezing tissues to be prepared for TEM. The micrographs of the methcarn-fixed samples indicate a loss of Z-disk integrity, intermyofibrillar space, mitochondria structure, and lipids. Ultimately, methacarn is not a viable primary fixative for tissue sample preparation for TEM. Similarly, liquid nitrogen freezing of samples wrapped in aluminum foil produced non-uniform Z-disk alignments that appeared smeared with swollen mitochondria. DMSO coating before freezing appears to lessen the alterations to contractile and mitochondrial morphological structures. DMSO appears to be useful for preserving the ultrastructure of sarcomeres if samples are covered before freezing.


Assuntos
Dimetil Sulfóxido , Tetróxido de Ósmio , Ácido Acético , Alumínio , Clorofórmio , Criopreservação , Fixadores/farmacologia , Glutaral , Gelo , Metanol , Microscopia Eletrônica de Transmissão , Músculos
18.
19.
Environ Pollut ; 311: 119921, 2022 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-35973450

RESUMO

Distribution in ice is regarded as one of important transport modes for pollutants in seasonal freeze-up waters in cold regions. However, the distribution characteristics and mechanisms of fluorinated antibiotics as emerging contaminants during the water freezing process remain unclear. Here, florfenicol and norfloxacin were selected as model fluorinated antibiotics to investigate their ice-water distribution. Effects of antibiotic molecular structure on the distribution were explored through comparative studies with their non-fluorinated structural analogs. Results showed that phase changes during the ice growth process redistributed the antibiotics, with antibiotic concentrations in water 3.0-6.4 times higher than those in ice. The solute-rich boundary layer with a concentration gradient was presented at the ice-water interface and controlled by constitutional supercooling during the freezing process. The ice-water distribution coefficient (KIW) values of antibiotics increased by 34.8%-38.0% with a doubling of the cooling area. The solute distribution coefficient (Kbs) values of antibiotics at -20 °C were 65.6%-70.3% higher than at -10 °C. The KIW and Kbs values of all antibiotics were negatively correlated with their water solubilities. The fluorine substituents influenced the binding energies between antibiotics and ice, resulting in a 1.1-fold increase in the binding energy of norfloxacin on the ice surface relative to its structural analog pipemidic acid. The results provide a new insight into the transport behaviors of fluorinated pharmaceuticals in ice-water systems.


Assuntos
Gelo , Norfloxacino , Antibacterianos , Flúor , Congelamento , Tianfenicol/análogos & derivados
20.
Phys Chem Chem Phys ; 24(35): 21165-21177, 2022 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-36039891

RESUMO

Antifreeze glycoproteins (AFGPs) inhibit ice recrystallization by a mechanism remaining largely elusive. The dynamics of AFGPs' hydration water and its involvement in the antifreeze activity, for instance, have not been identified conclusively. We herein, by simulation and theory, examined the picosecond site-specific water dynamics in the first hydration layer of a solvated AFGP8. Using a hydrogen bond switch event-based treatment, we strictly excluded the non-first layer water contribution. The observed water dynamics is much more retarded and inhomogeneous compared to the result of other commonly adopted treatments with non-first layer water contributions included. A molecular jump model analysis, with the cross-correlation between hydrogen bond switch molecular frames included, further indicates that excluding the non-first layer water contribution enhances the slow component in water dynamics, which couples strongly with the local environment. Further comparison with the structured ubiquitin protein revealed that, although the overall relaxation time distributions are similar between two proteins, a significant portion (>30%) of water hydrogen bond switching processes on the AFGP8 surface are considerably slower since they are trapped between the disaccharides and other protein regions. AFGP8 therefore resembles much the situation of an enzyme binding cleft or a DNA groove, where considerable slowdown of hydration water dynamics is observed due to the confinement. When bound to the ice surface, these slow, disordered water molecules may become a factor hindering the ice growth.


Assuntos
Gelo , Água , Proteínas Anticongelantes/química , Ligação de Hidrogênio , Modelos Moleculares , Simulação de Dinâmica Molecular , Água/química
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