Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 19 de 19
Filtrar
1.
J Clin Nurs ; 31(23-24): 3550-3559, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34935230

RESUMO

AIMS: The purpose of this study was to construct a model for oral assessment using deep learning image recognition technology and to verify its accuracy. BACKGROUND: The effects of oral care on older people are significant, and the Oral Assessment Guide has been used internationally as an effective oral assessment tool in clinical practice. However, additional training, education, development of user manuals and continuous support from a dental hygienist are needed to improve the inter-rater reliability of the Oral Assessment Guide. DESIGN: A retrospective observational study. METHODS: A total of 3,201 oral images of 114 older people aged >65 years were collected from five dental-related facilities. These images were divided into six categories (lips, tongue, saliva, mucosa, gingiva, and teeth or dentures) that were evaluated by images, out of the total eight items that comprise components of the Oral Assessment Guide. Each item was classified into a rating of 1, 2 or 3. A convolutional neural network, which is a deep learning method used for image recognition, was used to construct the image recognition model. The study methods comply with the STROBE checklist. RESULTS: We constructed models with a classification accuracy of 98.8% for lips, 94.3% for tongue, 92.8% for saliva, 78.6% for mucous membranes, 93.0% for gingiva and 93.6% for teeth or dentures. CONCLUSIONS: Highly accurate diagnostic imaging models using convolutional neural networks were constructed for six items of the Oral Assessment Guide and validated. In particular, for the five items of lips, tongue, saliva, gingiva, and teeth or dentures, models with a high accuracy of over 90% were obtained. RELEVANCE TO CLINICAL PRACTICE: The model built in this study has the potential to contribute to obtain reproducibility and reliability of the ratings, to shorten the time for assessment, to collaborate with dental professionals and to be used as an educational tool.


Assuntos
Lista de Checagem , Redes Neurais de Computação , Humanos , Idoso , Reprodutibilidade dos Testes , Estudos Retrospectivos
2.
Langmuir ; 36(17): 4695-4701, 2020 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-32283938

RESUMO

We studied the effects of temperature and shear flow on the structures of α-gel bilayers and domains. The α-gel samples were prepared by a carboxylate-type gemini surfactant synthesized from oleic acid and a long-chain alcohol (1-tetradecanol) with water. The structural change as a function of temperature was investigated using small- and wide-angle X-ray scattering (SWAXS) measurements, spin-spin relaxation time (T2) measurements, and optical microscopy observations. SWAXS measurements suggested that the decreased temperature yielded the α-gel phase from a lamellar liquid-crystal phase. We also found that the lamellar d-spacing drastically decreased at the phase transition temperature. The T2 measurements suggested that two kinds of protons with different mobilities coexisted in amphiphiles consisting of lamellar bilayers. The abundance of the protons with low mobility increased with decreasing temperature. Optical microscopy results indicated that the size of the α-gel domains increased with decreasing temperature. We assumed that the increased abundance of the low-mobility protons, indicating low flexibility of lamellar bilayers, led to a decreased lamellar d-spacing and increased size of the α-gel domains. Shear-induced structural changes in the α-gel were also studied using simultaneous small-angle neutron scattering and rheological measurements. The α-gel can maintain bilayer structures even at high shear rates. We also found that the lamellar d-spacing was independent of the shear rate.

3.
J Oleo Sci ; 68(6): 567-572, 2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31092796

RESUMO

We characterized the friction and adsorption properties of an oleic acid-based gemini amphiphile having two carboxylic acid headgroups. We employed silica as a solid material, and diethyl sebacate and bis (2-ethylhexyl) sebacate as polar ester oils. Oleic acid and stearic acid were used as comparative amphiphilic materials. These amphiphiles were soluble in the ester oils, and the solubility of the gemini amphiphile was lower than that of the other two amphiphiles. Quartz crystal microbalance with dissipation monitoring measurements suggested that the gemini amphiphile had greater adsorption capability than the two comparative amphiphiles. The greater adsorption density of the gemini amphiphile resulted in the formation of a rigid interfacial film, as suggested by the normal force curves obtained by atomic force microscopy (AFM). We assessed the friction property of these systems using a ball-on-plate-type friction analyzer and by friction-mode AFM (friction force curve). These measurements confirmed that the gemini amphiphile had a smaller kinetic friction coefficient than that of the other two amphiphiles. These results suggest the potential of the gemini amphiphile as a friction modifier in polar oils.


Assuntos
Adsorção , Calcitriol/análogos & derivados , Ácidos Decanoicos/química , Fricção , Ácido Oleico/química , Dióxido de Silício/química , Ácidos Esteáricos/química , Tensoativos/química , Calcitriol/química , Ácidos Carboxílicos , Solubilidade
4.
Biochemistry ; 57(28): 4177-4185, 2018 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-29936828

RESUMO

Protein tyrosine sulfation (PTS) is a post-translational modification regulating numerous biological events. PTS generally occurs at flexible regions of proteins, enhancing intermolecular interactions between proteins. Because of the high flexibility associated with the regions where PTS is generally encountered, an atomic-level understanding has been difficult to achieve by X-ray crystallography or nuclear magnetic resonance techniques. In this study, we focused on the conformational behavior of a flexible sulfated peptide and its interaction with an antibody. Molecular dynamics simulations and thermodynamic analysis indicated that PTS reduced the main-chain fluctuations upon the appearance of sulfate-mediated intramolecular H-bonds. Collectively, our data suggested that one of the mechanisms by which PTS may enhance protein-protein interactions consists of the limitation of conformational dynamics in the unbound state, thus reducing the loss of entropy upon binding and boosting the affinity for its partner.


Assuntos
Anticorpos/metabolismo , Peptídeos/metabolismo , Tirosina/análogos & derivados , Anticorpos/química , Cristalografia por Raios X , Simulação de Dinâmica Molecular , Peptídeos/química , Ligação Proteica , Mapas de Interação de Proteínas , Processamento de Proteína Pós-Traducional , Termodinâmica , Tirosina/química , Tirosina/metabolismo
5.
Phys Chem Chem Phys ; 20(13): 8874-8880, 2018 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-29546256

RESUMO

In this study, we synthesize a novel oleic acid-based gemini surfactant with carboxylate headgroups, and study the effect of stereochemistry (anti- vs. syn-) on self-aggregation properties in water. We investigate these properties using phase diagrams, static surface tension, and one-dimensional and two-dimensional nuclear magnetic resonance (NMR) measurements. We find that a phase transition from a hexagonal liquid crystal (H1) phase to a lamellar liquid crystal (Lα) phase occurs at a lower surfactant concentration in the syn form, when compared with the anti form. In addition, the syn form gemini surfactant forms micelles with a close packing of the headgroups via hydrogen bonding. This was supported by static surface tensiometry; the area occupied by surfactant molecules at the air/aqueous solution interface is smaller for the syn form than for the anti form. We propose that, for the syn form gemini surfactant, the closer packing of the headgroups as well as the hydrogen bonding network around the micelle interface prevent water penetration into the hydrophobic part of the micelle.

6.
Neurol Med Chir (Tokyo) ; 57(11): 607-611, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-28931766

RESUMO

The p.R4810K (rs11273543, c.14429G > A) variant of the RNF213 gene is associated with increased risk of Moyamoya disease (MMD), which is an idiopathic progressive intracranial vascular steno-occlusive disease, in Asian populations. Numerous variant association studies for this MMD variant have been performed in Japan to date. Since another genetic study that utilized approximately 140,000 single nucleotide polymor (SNPs) has indicated that there still are genetic differences among mainland Japanese, there is a possibility that the variant distribution in patients with MMD and normal individuals varies between different Japanese regions. Additionally, the majority of variant association studies have used Sanger sequencing, which is labor-intensive, time-consuming, and costly. In this study, we analyzed the frequency of the variant genotype in patients with MMD and normal individuals in Kyushu using pyrosequencing, which is an accurate, cost-effective, and automated method. We found differences in the genotype frequencies in familial patients from Kyushu and normal populations in Tohoku compared with west Japan, which suggested that there were differences in the frequency of the variant among different regions in Japan.


Assuntos
Adenosina Trifosfatases/genética , Povo Asiático/genética , Genótipo , Doença de Moyamoya/genética , Ubiquitina-Proteína Ligases/genética , Adolescente , Adulto , Estudos de Casos e Controles , Criança , Feminino , Predisposição Genética para Doença/etnologia , Predisposição Genética para Doença/genética , Humanos , Japão , Masculino , Doença de Moyamoya/etnologia , Análise de Sequência de DNA , Adulto Jovem
7.
Am J Case Rep ; 17: 909-915, 2016 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-27904130

RESUMO

BACKGROUND Lymph node metastasis of hepatocellular carcinoma is rare, and lymph nodes located on hepatic hilar and hepatoduodenal ligaments are primary targets. Metastasis to a mesocolic lymph node has not been reported previously. CASE REPORT A 65-year-old woman with liver cirrhosis underwent primary resection of hepatocellular carcinoma. Two and a half years later, tumor marker levels increased remarkably and imaging revealed a mesocolic mass. The tumor measured 27 mm in diameter and showed characteristic findings consistent with hepatocellular carcinoma in dynamic computed tomographic images, although the tumor was negative in fluorine-18-fluorodeoxyglucose positron emission tomographic images. A preoperative diagnosis of solitary metastasis to a mesocolic lymph node was made, and we elected to perform surgical resection, although therapeutic strategies for rare solitary extrahepatic metastasis are controversial. The tumor was located in the mesocolon nearly at the wall of the descending colon. Curative resection was performed and histopathological analysis confirmed metastatic hepatocellular carcinoma to a mesocolic lymph node. Tumor marker levels normalized immediately postoperatively. To date, the patient remains free from recurrence without adjuvant therapy. CONCLUSIONS This is the first known case of solitary hepatocellular carcinoma metastasis to a distant mesocolic lymph node, successfully treated. Diagnosing solitary hepatocellular carcinoma metastases to distant lymph nodes can be difficult. Although the ideal therapeutic approach has not be defined, surgical resection of solitary metastatic lymph nodes may be beneficial in carefully selected cases.


Assuntos
Carcinoma Hepatocelular/secundário , Carcinoma Hepatocelular/cirurgia , Neoplasias Hepáticas/patologia , Mesocolo , Neoplasias Peritoneais/secundário , Neoplasias Peritoneais/cirurgia , Idoso , Carcinoma Hepatocelular/diagnóstico por imagem , Feminino , Humanos , Neoplasias Hepáticas/cirurgia , Neoplasias Peritoneais/diagnóstico por imagem , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada
8.
Front Immunol ; 7: 344, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27656184

RESUMO

Pentraxin 3 (PTX3) is a soluble pattern recognition molecule that plays critical roles in innate immunity. Its fundamental functions include recognition of microbes, activation of complement cascades, and opsonization. The findings that PTX3 is one of the component proteins in neutrophil extracellular traps (NETs) and binds with other NET proteins imply the importance of PTX3 in the NET-mediated trapping and killing of bacteria. As NETs play certain critically important host-protective roles, aberrant NET production results in tissue damage. Extracellular histones, the main source of which is considered to be NETs, are mediators of septic death due to their cytotoxicity toward endothelial cells. PTX3 protects against extracellular histones-mediated cytotoxicity through coaggregation. In addition to the anti-bacterial roles performed in coordination with other NET proteins, PTX3 appears to mitigate the detrimental effect of over-activated NETs. A better understanding of the role of the PTX3 complexes in NETs would be expected to lead to new strategies for maintaining a healthy balance between the helpful bactericidal and undesirable detrimental activities of NETs.

9.
World J Gastroenterol ; 22(47): 10287-10303, 2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-28058010

RESUMO

Laparoscopic cholecystectomy (LC) does not require advanced techniques, and its performance has therefore rapidly spread worldwide. However, the rate of biliary injuries has not decreased. The concept of the critical view of safety (CVS) was first documented two decades ago. Unexpected injuries are principally due to misidentification of human factors. The surgeon's assumption is a major cause of misidentification, and a high level of experience alone is not sufficient for successful LC. We herein describe tips and pitfalls of LC in detail and discuss various technical considerations. Finally, based on a review of important papers and our own experience, we summarize the following mandatory protocol for safe LC: (1) consideration that a high level of experience alone is not enough; (2) recognition of the plateau involving the common hepatic duct and hepatic hilum; (3) blunt dissection until CVS exposure; (4) Calot's triangle clearance in the overhead view; (5) Calot's triangle clearance in the view from underneath; (6) dissection of the posterior right side of Calot's triangle; (7) removal of the gallbladder body; and (8) positive CVS exposure. We believe that adherence to this protocol will ensure successful and beneficial LC worldwide, even in patients with inflammatory changes and rare anatomies.


Assuntos
Colecistectomia Laparoscópica/métodos , Protocolos Clínicos , Doenças Biliares/etiologia , Colecistectomia Laparoscópica/efeitos adversos , Competência Clínica , Procedimentos Cirúrgicos Eletivos , Humanos , Curva de Aprendizado , Segurança do Paciente , Fatores de Risco , Resultado do Tratamento
10.
J Oleo Sci ; 63(3): 257-67, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24712085

RESUMO

We have developed oleic acid-based partially fluorinated gemini surfactants with carboxylic acid headgroups. The fluorocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via a -CH(2)CH(2)OCO- unit, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via -OCOCH(2)CH(2)- units. The aqueous solution properties of these surfactants were studied at pH 9 in the presence of 10 mmol dm­3 NaCl by means of static surface tension, pyrene fluorescence, and dynamic light scattering measurements. The resulting surface tension data demonstrate that the partially fluorinated gemini surfactants exhibit excellent surface activity in their dilute aqueous solutions. In addition, the surfactants are suggested to form micellar aggregates 2­4 nm in diameter. We also studied the aqueous temperature-concentration phase diagrams of the partially fluorinated gemini surfactants (disodium salts) on the basis of visual observations (through a crossed polarizer), polarized optical microscopy, and small angle X-ray scattering measurements. Several phase states including micellar solution phase, hexagonal phase, bicontinuous cubic phase, and lamellar phase were observed along with the coexistence of these phases in certain regions. Assemblies with lesser positive curvature tend to be formed with increasing surfactant concentration, increasing temperature, and increasing fluorocarbon chain length. A comparison of the phase diagrams of the partially fluorinated and hydrogenated surfactant systems suggests that close molecular packing is inhibited within the assemblies of the partially fluorinated surfactants because of the limited miscibility between the fluorocarbon and hydrocarbon units. To the best of our knowledge, this is the first systematic report focusing on the temperature-concentration phase diagrams of (partially) fluorinated gemini surfactants over a wide range of compositions and temperatures.


Assuntos
Calcitriol/análogos & derivados , Fenômenos Químicos , Halogenação , Ácido Oleico/química , Transição de Fase , Tensoativos/química , Calcitriol/química , Ácidos Carboxílicos/química , Fluorocarbonos/química , Concentração de Íons de Hidrogênio , Cristais Líquidos , Micelas , Soluções , Tensão Superficial , Temperatura , Água
11.
J Oleo Sci ; 62(7): 489-98, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23823915

RESUMO

Cationic gemini surfactants having a quaternary ammonium headgroup have been synthesized from oleic acid. The hydrocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via an amide bond, while the quaternary ammonium headgroup is introduced onto the cis double bond of oleic acid. The Krafft temperature of these surfactants drops below room temperature (ca. 25°C) when the counterion is exchanged from Br⁻ to Cl⁻. The aqueous solution properties of the Cl series of surfactants have been assessed by means of pyrene fluorescence, dynamic light scattering (DLS), and static surface tension measurements. An increased hydrocarbon chain length results in a lower critical micelle concentration (cmc) and a higher adsorption efficiency at the air/aqueous solution interface. Surface tension measurements suggest the formation of premicelles at concentrations below cmc, whereas, above cmc, DLS indicates the formation of micellar aggregates whose diameter ranges from 5 to 10 nm. We, furthermore, characterized the adsorption of these surfactants to the silica/aqueous solution interface and observed their spontaneous adsorption to the solid surface by electrostatic and intermolecular hydrophobic interactions. The combination of soft-contact imaging atomic force microscopy (AFM) and force-curve data suggests bilayer formation above cmc, which is reflective of the large packing parameter of the gemini surfactants. Interestingly, we found the repulsive interaction observed during compression of the adsorbed layer to be relatively weak, as a result of the low adsorption density and/or the loose molecular packing arrangement, which arises from the asymmetric structure.


Assuntos
Micelas , Ácido Oleico/química , Compostos de Amônio Quaternário/química , Dióxido de Silício/química , Tensoativos/química , Adsorção , Interações Hidrofóbicas e Hidrofílicas , Compostos de Amônio Quaternário/síntese química , Eletricidade Estática , Tensoativos/síntese química
12.
Chem Commun (Camb) ; 48(49): 6130-2, 2012 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-22588181

RESUMO

Titanate nanofunnel brushes were grown on sol-gel derived amorphous TiO(2) thin films, whose shape can be tuned from nanosheets to nanofunnels by changing hydrothermal conditions. A superhydrophobic adhesive surface was achieved by a chemical modification of the brushes.

13.
J Oleo Sci ; 60(8): 411-7, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21768742

RESUMO

Anionic gemini surfactants with carboxylic acid headgroups have been synthesized from oleic acid. The hydrocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via an ester bond, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via disuccinyl units. The surfactants exhibit pH-dependent protonation-deprotonation behavior in aqueous solutions. In alkaline solutions (pH 9 in the presence of 10 mmol dm(-3) NaCl as the background electrolyte), the surfactants can lower the surface tension as well as form molecular assemblies, even in the region of low surfactant concentrations. Under acidic (pH 3) or neutral (pH 6-7) conditions, the surfactants are intrinsically insoluble in aqueous media and form a monolayer at the air/water interface. In this study, we have investigated physicochemical properties such as the function of the hydrocarbon chain length by means of static surface tension, pyrene fluorescence, dynamic light scattering, surface pressure-area isotherms, and infrared external reflection measurements.


Assuntos
Ácidos Carboxílicos/química , Ácido Oleico/química , Ácido Oleico/síntese química , Tensoativos/química , Tensoativos/síntese química , Ácidos/química , Fluorescência , Hidrodinâmica , Concentração de Íons de Hidrogênio , Pirenos/química , Soluções , Espectrofotometria Infravermelho , Tensão Superficial , Temperatura , Titulometria
14.
J Oleo Sci ; 59(10): 541-8, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-20877147

RESUMO

Novel anionic heterogemini surfactants have been synthesized from two kinds of unsaturated fatty acids (oleic acid and petroselinic acid). The hydrocarbon chain is covalently bound to the terminal carbonyl group of the unsaturated fatty acids and hydrophilic headgroups (i.e., sulfonic and hydroxyl groups) are introduced to the cis double bond. The aqueous solution properties of the surfactants synthesized here have been studied on the basis of static/dynamic surface tension, conductivity, fluorescence, and dynamic light scattering (DLS) data. We have mainly focused on the following two factors that may significantly impact the aqueous solution properties of the surfactants: one is hydrocarbon chain length and the other is molecular symmetry. The first key result from our current study is that increased hydrocarbon chain length results in a closely packed monolayer film at the air/aqueous solution interface, even at low concentrations as a result of the increased hydrophobicity of the longer chain analogue. We have previously observed a similar trend when aqueous solution properties of oleic acid-based phosphate-type heterogemini surfactants were studied. The second key finding of our current research is that increased molecular symmetry results in greater surface activities (which include lower aqueous surface tension and greater molecular packing at the air/aqueous solution interface). In addition, it seems likely that the size of molecular assemblies spontaneously formed in bulk solution decreases when the molecular symmetry increases. These results suggest that the symmetric analogue provides greater hydrophobic environments, although the exact reason for this is not yet known.


Assuntos
Radical Hidroxila/química , Ácido Oleico/química , Ácidos Oleicos/química , Ácidos Sulfônicos/química , Tensoativos/síntese química , Estrutura Molecular , Estereoisomerismo , Tensoativos/química
15.
J Colloid Interface Sci ; 338(1): 229-35, 2009 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-19586636

RESUMO

The physicochemical properties of aqueous solutions of novel anionic heterogemini surfactants (POH-n-ODAm) have been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The surfactants are synthesized from oleic acid: the hydrocarbon chain (n=6, 8 and 10) is covalently bound to the terminal carbonyl group and a phosphate headgroup is introduced to the cis double bond of an oleic acid derivative. The static surface tension and fluorescence measurements demonstrate that the critical aggregation concentration (cac) is decreased significantly with increasing hydrocarbon chain length, resulting from the increased hydrophobicity and the increased degree of dissymmetry of the surfactants. As is generally seen for gemini surfactants, the measured cac is much lower than that of the monomeric phosphate-type surfactant reported previously. At concentrations well above the cac, the heterogemini surfactants spontaneously form vesicular assemblies in bulk solution, which is confirmed with DLS and cryo-TEM measurements.

16.
J Oleo Sci ; 58(8): 403-13, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19584566

RESUMO

A novel polymerizable anionic gemini surfactant has been synthesized and the physicochemical properties in aqueous solution have been studied with a combination of various analytical techniques. The surfactant (PA12-2-12) contains two anionic monomeric parts linked with an ethylene spacer and polymerizable methacryloxy groups covalently bound to the terminal of the hydrocarbon chains. The static surface tension data suggest that, when compared with a conventional (non-polymerizable) anionic gemini surfactant (A12-2-12), (i) the interfacial adsorption of PA12-2-12 occurs more effectively from low surfactant concentrations, whereas (ii) a weak interaction of the polymerizable terminal groups with water molecules (and/or the steric hindrance of the polymerizable groups) plays a significant role in the subsequent molecular packing at the air/aqueous solution interface. The latter effect (as well as the electrostatic repulsion between the anionic headgroups) results in a relatively less packed monolayer film, overcoming the strong intermolecular attractive interaction that is frequently seen for gemini surfactant systems. In the region of low added electrolyte concentrations, PA12-2-12 spontaneously forms spherical micelles in aqueous solution, which is confirmed with the Corrin-Harkins analysis (critical micelle concentration (cmc) vs. total counter-ion concentration) and cryogenic transmission electron microscopy (cryo-TEM). The spherical micelles have been polymerized under UV light irradiation in the absence of added electrolytes. Cryo-TEM measurements confirm that no significant change in the original micelle morphology occurs during the polymerization. This offers a possibility that the polymerizable anionic gemini surfactant should be useful as nano-structural organic templates and/or interfacial stabilizers in aqueous solution.


Assuntos
Polímeros/química , Polímeros/síntese química , Tensoativos/química , Tensoativos/síntese química , Ânions/síntese química , Ânions/química , Físico-Química , Microscopia Crioeletrônica , Eletrólitos/química , Etilenos/química , Hidrocarbonetos/química , Metacrilatos/química , Micelas , Estrutura Molecular , Tamanho da Partícula , Soluções , Eletricidade Estática , Propriedades de Superfície , Água/química
17.
J Oleo Sci ; 57(8): 423-9, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18622125

RESUMO

Adsorption of a cationic gemini surfactant (1,2-bis(dodecyldimethylammonio) ethane dibromide, 12-2-12) and the corresponding monomeric surfactant (dodecyltrimethylammonium bromide, DTAB) on montmorillonite has been characterized with a combination of adsorption isotherm, interlayer spacing and FT-IR spectroscopic data. Adsolubilization of vitamin E into the adsorbed surfactant layers has also been studied. The adsorption isotherm data reveal that the adsorption of the two surfactants is driven by the two factors: one is the cation exchange that occurs on the interlayer basal planes and the other is the hydrophobic interaction between hydrocarbon chains of the surfactants. Although the adsorbed amount measured in the saturation region (in mol g(-1)) is almost identical for the two surfactants, the conformation of the intercalated surfactant molecules differs significantly from each other. The adsorption of DTAB results in a lateral bilayer arrangement in the limited interlayer space, whereas 12-2-12 gives a normal bilayer arrangement in the expanded interlayer space. Adsolubilization of vitamin E takes place into the adsorbed surfactant layers, and interestingly, all the vitamin E molecules added in the montmorillonite suspensions are hybridized at lower surfactant concentrations due to the great specific surface area of the clay material. Since the maximum adsolubilization amount is usually obtained just below the critical micelle concentration, the gemini surfactant is deemed to be more efficient than the corresponding monomeric one to achieve the great adsolubilization amount.


Assuntos
Bentonita/química , Compostos de Amônio Quaternário/química , Tensoativos/química , Tocoferóis/química , Adsorção , Cátions/química , Interações Hidrofóbicas e Hidrofílicas , Micelas , Tamanho da Partícula , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
18.
J Colloid Interface Sci ; 318(2): 440-8, 2008 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-18031755

RESUMO

The adsorption and micellization behavior of novel sugar-based gemini surfactants (N,N(')-dialkyl-N,N(')-digluconamide ethylenediamine, Glu(n)-2-Glu(n), where n is the hydrocarbon chain length of 8, 10 and 12) has been studied on the basis of static/dynamic surface tension, fluorescence, dynamic light scattering (DLS) and cryogenic transmission electron microscope (cryo-TEM) data. The static surface tension of the aqueous Glu(n)-2-Glu(n) solutions measured at the critical micelle concentration (cmc) is observed to be significantly lower than that of the corresponding monomeric surfactants. This suggests that the gemini surfactants, newly synthesized in the current study, are able to form a closely packed monolayer film at the air/aqueous solution interface. The greater ability in the molecular association is supported by the remarkably (approximately 100-200 times) lower cmc of the gemini surfactants compared with the corresponding monomeric ones. With a combination of the fluorescence and DLS data, a structural transformation of the Glu(n)-2-Glu(n) micelles is suggested to occur with an increase in the concentration. The cryo-TEM measurements clearly confirm the formation of worm-like micelles of Glu(12)-2-Glu(12) at the concentration well above the cmc.


Assuntos
Calcitriol/análogos & derivados , Gluconatos/química , Micelas , Tensoativos/química , Adsorção , Ar , Calcitriol/química , Microscopia Crioeletrônica , Fluorescência , Estrutura Molecular , Tamanho da Partícula , Espalhamento de Radiação , Soluções/química , Tensão Superficial , Água/química
19.
J Mass Spectrom ; 37(2): 209-15, 2002 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-11857765

RESUMO

Calditocaldarchaeol (neutral tetraether lipid) from Sulfolobus acidocaldarius (acidothermophilic archaea) and intact total lipid from the thermoacidophilic archaea Sulfolobus sp. was examined by electrospray ionization time-of-flight mass spectrometry in the negative-ion mode using high resolution. When the sample was injected as a solution in a 3:1 mixture of methanol (MeOH) and chloroform (CHCl(3)) using an infusion system, the total ether lipid afforded molecular-related ions as [M - H](-) for acidic polar lipids containing a phosphoric or sulfuric group, and as [M + Cl](-) ion for neutral glycolipids. The attachment of chloride was confirmed by the observation of [M + Br](-) ion, instead of [M + Cl](-) ion, when a 3:1 mixture of MeOH and CHBr(3) was used in place of MeOH-CHCl(3) as the solvent. The composition of tetraether neutral glycolipids that are different from each other only in the number of five-membered rings in the isoprenoid chain was determined on the basis of the isotope-resolved mass spectrum of [M + Cl](-) ions. As for acidic tetraether lipids, molecular-related ions [M - H](-)) were not observed when the 3:1 MeOH-CHBr(3) mixture was used as the solvent. These results together afforded a facile method of distinguishing neutral from acidic tetraether lipids in intact total lipids of acidothermophilic archaea. This method was applied to determine the difference of the number of five-membered rings in isoprenyl chains of neutral tetraether glycolipids yielded by the Sulfolobus sp. grown at different temperatures. Discrimination of neutral tetraether glycolipids from acidic tetraether lipids in the total lipids obtained from Thermoplasma sp. was also achieved by this method.


Assuntos
Éteres de Glicerila/análise , Halogênios/química , Lipídeos de Membrana/análise , Espectrometria de Massas por Ionização por Electrospray/métodos , Sulfolobus/química , Thermoplasma/química , Animais , Íons/química , Estrutura Molecular
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA