scholarly journals Influence of Dodecyltrimethylammonium Halides on Thermotropic Phase Behaviour of Phosphatidylcholine/Cholesterol Bilayers

2000 ◽  
Vol 55 (9-10) ◽  
pp. 753-757 ◽  
Author(s):  
Bożenna Różycka-Roszak ◽  
Hanna Pruchnik
Keyword(s):  
Phase 1 ◽  
Phase Behaviour ◽  
Water Phase ◽  
Lipid Phase ◽  
Dodecyltrimethylammonium Bromide ◽  
Phase 2 ◽  
H Nmr ◽  
Dodecyltrimethylammonium Chloride ◽  
Series Of Experiments ◽  
Mixed Film

Abstract Effects of dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium iodide (DTAI) on thermotropic phase behaviour of phosphatidylcholine bilayers containing cholesterol as well as on 1H NMR spectra were studied. Two series of experiments were performed. In the first one the surfactants were added to the water phase while in the other directly to the lipid phase (a mixed film from cholesterol, surfactant and phosphatidylcholine was formed). The effects of particular surfactants on the main phase transition temperature, Tm, were more pronounced when added to the lipid phase (2nd method) than to the water phase ( 1st method); the opposite happened when cholesterol was absent (Różycka-Roszak and Pruchnik 2000, Z. Naturforsch. 55c, 240-244). Furthermore, in the case of the first method the transitions were asymmetrical while in the second method nearly symmetrical. It is suggested that surfactant poor and surfactant rich domains are formed when surfactants are added to the water phase.

Effect of Counterions on the Influence of Dodecyltrimethylammonium Halides on Thermotropic Phase Behaviour of Phosphatidylcholine Bilayers

2000 ◽  
Vol 55 (3-4) ◽  
pp. 240-244 ◽  
Author(s):  
Bożenna Różycka-Roszak ◽  
Hanna Pruchnik
Keyword(s):  
Phase 1 ◽  
Water Structure ◽  
Phase Behaviour ◽  
Water Phase ◽  
Lipid Phase ◽  
Dodecyltrimethylammonium Bromide ◽  
H Nmr ◽  
Dodecyltrimethylammonium Chloride ◽  
Series Of Experiments ◽  
Mixed Film

Abstract Effects of dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium iodide (DTAI) on thermotropic phase behaviour of phosphatidylcholine bilayers as well as on 1H NMR spectra were studied. In order to enhance the effect of counterions on water structure two series of experiments were performed. In the first one the surfactants were added to the water phase and in the other one directly to lipid phase (a mixed film was formed). The effects of particular surfactants on the main phase-transition temperature were more pronounced when they were added to the water phase (1st method) instead of the lipid phase (2nd method). Furthermore, in the case of the first method the transitions were found asymmetrical while in the second method nearly symmetrical. It is suggested that surfactant-poor and surfactant-rich domains are formed when surfactants are added to the water phase.

Influence of Dodecyltrimethylammonium Halides on Interaction of Phenyltin Compounds with Model Membranes

2001 ◽  
Vol 56 (7-8) ◽  
pp. 623-628
Author(s):  
Bożenna Różycka-Roszak ◽  
Hanna Pruchnik
Keyword(s):  
Phase Formation ◽  
Nmr Spectra ◽  
Structural Changes ◽  
Hexagonal Phase ◽  
Model Membranes ◽  
Phase Behaviour ◽  
Dodecyltrimethylammonium Bromide ◽  
H Nmr ◽  
Dodecyltrimethylammonium Chloride ◽  
Triphenyltin Chloride

The effects were studied of dodecyltrimethylammonium chloride (DTAC), dodecyltrimethylammonium bromide (DTAB) and dodecyltrimethylammonium iodide (DTAI) on thermo­tropic phase behaviour of phosphatidylcholine bilayers, as well as on 1H NMR and 31P NMR spectra, in the presence of diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT). The obtained results indicate that in the presence of the surfactant studied the interaction of phenyltin compounds with model membranes was changed and the changes depended on the kind of the counterion. The surfactants studied (especially DTAC) decrease the ability of phenyltin compounds to induce structural changes in the bilayer. It is suggested that DTAB, and especially DTAC, prevent DPhT induced interdigitated phase formation as well as formation of an inverted hexagonal phase (HII) in the case of TPhT/DPPC liposomes

The Influence of Cholesterol on the Interaction between N-Dodecyl-N,Ndimethyl- N-benzylammonium Halides and Phosphatidylcholine Bilayers

2006 ◽  
Vol 61 (3-4) ◽  
pp. 302-308 ◽  
Author(s):  
Bożenna Różycka-Roszak ◽  
Adriana Przyczyna ◽  
Paweł Misiak ◽  
Hanna Pruchnik
Keyword(s):  
Phase Transition ◽  
Phase Behavior ◽  
Liquid State ◽  
Membrane Structure ◽  
Nmr Spectra ◽  
Phospholipid Bilayer ◽  
Water Phase ◽  
Lipid Phase ◽  
H Nmr ◽  
Mixed Film

Effects of N-dodecyl-N,N-dimethyl-N-benzylammonium halides (DBeAX) on thermotropic phase behavior of phosphatidylcholine/cholesterol bilayers as well as on 1H NMR spectra were studied. The surfactants were added either to the water phase or directly to the lipid phase (a mixed film was formed). The benzyl group, opposite to liposomes without cholesterol, is not incorporated into the bilayer in the gel state but only in the liquid state. All the halides DBeAX (particularly the chloride DBeAC) showed greater ability to destabilize the membrane structure in the presence than in the absence of cholesterol. The interaction of DBeAX with DPPC/cholesterol bilayers and subsequent changes in the phospholipid bilayer organization depended on the kind of counterion. The strongest effects were observed for chloride (most electronegative ion) and for iodide (largest ion). The effects of chloride and bromide on phase transition and 1H NMR spectra in the presence and absence of cholesterol were opposite. This is discussed in terms of the influence of counterions on the pair cholesterol-DPPC interactions.

Shell Movements of the Freshwater Mussel, Hyridella australis Lam. (Lamellibranchiata)

1950 ◽  
Vol 1 (2) ◽  
pp. 259 ◽  
Author(s):  
ID Hiscock
Keyword(s):  
Mathematical Proof ◽  
Phase 1 ◽  
Freshwater Mussel ◽  
Continuous Illumination ◽  
Phase 2 ◽  
Phase 3 ◽  
Two Phase ◽  
Feeding Rhythm ◽  
Series Of Experiments ◽  
Light Rhythm

An analysis of about 4,500 hours of shell movement tracings of the freshwater mussel, Hyridella australis Lam., is presented. Nine series of experiments have been conducted, representing variations in light and temperature conditions. It has been found that, as well as shell movements, shell position or degree of openness must be considered. The shells may be closed (phase 1), completely open (phase 3), or stationary, intermediate between the two (phase 2), for the validity of which position mathematical proof has been found. The characteristics of each phase have been outlined. Temperature, within the range 17 to 27°C shows no well-definded influence on shell movements or the degree of openness. The influence of light, especially in regard to phase 2, is discussed. A diurnal light rhythm is associated with a diurnal feeding rhythm; under continuous illumination the shells tend to remain apart but in phase 2, darkness suppresses shell movements and feeding. The shell movements during ovulation are discussed.

scholarly journals Were all trilobites fully marine? Trilobite expansion into brackish water during the early Palaeozoic

2021 ◽  
Vol 288 (1944) ◽  
pp. 20202263
Author(s):  
M. Gabriela Mángano ◽  
Luis A. Buatois ◽  
Beatriz G. Waisfeld ◽  
Diego F. Muñoz ◽  
N. Emilio Vaccari ◽  
...  
Keyword(s):  
Salinity Stress ◽  
Brackish Water ◽  
Phase 1 ◽  
Water Phase ◽  
Marine Environments ◽  
Phase 2 ◽  
Early Palaeozoic ◽  
Body Fossil ◽  
Early Late ◽  
Tolerance To Salinity

Trilobites, key components of early Palaeozoic communities, are considered to have been invariably fully marine. Through the integration of ichnological, palaeobiological, and sedimentological datasets within a sequence-stratigraphical framework, we challenge this assumption. Here, we report uncontroversial trace and body fossil evidence of their presence in brackish-water settings. Our approach allows tracking of some trilobite groups foraying into tide-dominated estuaries. These trilobites were tolerant to salinity stress and able to make use of the ecological advantages offered by marginal-marine environments migrating up-estuary, following salt wedges either reflecting amphidromy or as euryhaline marine wanderers. Our data indicate two attempts of landward exploration via brackish water: phase 1 in which the outer portion of estuaries were colonized by olenids (Furongian–early late Tremadocian) and phase 2 involving exploration of the inner to middle estuarine zones by asaphids (Dapingian–Darriwilian). This study indicates that tolerance to salinity stress arose independently among different trilobite groups.

Rationalization and internalization

2001 ◽  
Vol 60 (4) ◽  
pp. 215-230 ◽  
Author(s):  
Jean-Léon Beauvois
Keyword(s):  
Phase 1 ◽  
Facilitatory Effect ◽  
Phase 2 ◽  
Causal Explanations ◽  
Reduction Effect ◽  
Dissonance Reduction

After having been told they were free to accept or refuse, pupils aged 6–7 and 10–11 (tested individually) were led to agree to taste a soup that looked disgusting (phase 1: initial counter-motivational obligation). Before tasting the soup, they had to state what they thought about it. A week later, they were asked whether they wanted to try out some new needles that had supposedly been invented to make vaccinations less painful. Agreement or refusal to try was noted, along with the size of the needle chosen in case of agreement (phase 2: act generalization). The main findings included (1) a strong dissonance reduction effect in phase 1, especially for the younger children (rationalization), (2) a generalization effect in phase 2 (foot-in-the-door effect), and (3) a facilitatory effect on generalization of internal causal explanations about the initial agreement. The results are discussed in relation to the distinction between rationalization and internalization.

PENERAPAN MODEL QUANTUM LEARNING UNTUK MENINGKATKAN HASIL BELAJAR AUTOCAD SISWA KELAS X TEKNIK PEMESINAN SMK NEGERI 1 STABAT

2013 ◽  
Vol 5 (1) ◽  
Author(s):  
Abdul Hasan Saragih
Keyword(s):  
Positive Response ◽  
Phase 1 ◽  
First Grade ◽  
Learning Model ◽  
Second Phase ◽  
Phase 2 ◽  
Phase 3 ◽  
The Third ◽  
Third Phase ◽  
Quantum Learning

This classroom research was conducted on the autocad instructions to the first grade of mechinary class of SMK Negeri 1 Stabat aiming at : (1) improving the student’ archievementon autocad instructional to the student of mechinary architecture class of SMK Negeri 1 Stabat, (2) applying Quantum Learning Model to the students of mechinary class of SMK Negeri 1 Stabat, arising the positive response to autocad subject by applying Quantum Learning Model of the students of mechinary class of SMK Negeri 1 Stabat. The result shows that (1) by applying quantum learning model, the students’ achievement improves significantly. The improvement ofthe achievement of the 34 students is very satisfactory; on the first phase, 27 students passed (70.59%), 10 students failed (29.41%). On the second phase 27 students (79.41%) passed and 7 students (20.59%) failed. On the third phase 30 students (88.24%) passed and 4 students (11.76%) failed. The application of quantum learning model in SMK Negeri 1 Stabat proved satisfying. This was visible from the activeness of the students from phase 1 to 3. The activeness average of the students was 74.31% on phase 1,81.35% on phase 2, and 83.63% on phase 3. (3) The application of the quantum learning model on teaching autocad was very positively welcome by the students of mechinary class of SMK Negeri 1 Stabat. On phase 1 the improvement was 81.53% . It improved to 86.15% on phase 3. Therefore, The improvement ofstudent’ response can be categorized good.

In situ deteriorating patient simulation in general practice

2020 ◽  
Vol 70 (suppl 1) ◽  
pp. bjgp20X711425
Author(s):  
Joanna Lawrence ◽  
Petronelle Eastwick-Field ◽  
Anne Maloney ◽  
Helen Higham
Keyword(s):  
Life Support ◽  
Early Recognition ◽  
Phase 1 ◽  
Patient Simulation ◽  
Medical Emergency ◽  
Phase 2 ◽  
Action Plans ◽  
Integrated Simulation ◽  
Deteriorating Patient

BackgroundGP practices have limited access to medical emergency training and basic life support is often taught out of context as a skills-based event.AimTo develop and evaluate a whole team integrated simulation-based education, to enhance learning, change behaviours and provide safer care.MethodPhase 1: 10 practices piloted a 3-hour programme delivering 40 minutes BLS and AED skills and 2-hour deteriorating patient simulation. Three scenarios where developed: adult chest pain, child anaphylaxis and baby bronchiolitis. An adult simulation patient and relative were used and a child and baby manikin. Two facilitators trained in coaching and debriefing used the 3D debriefing model. Phase 2: 12 new practices undertook identical training derived from Phase 1, with pre- and post-course questionnaires. Teams were scored on: team working, communication, early recognition and systematic approach. The team developed action plans derived from their learning to inform future response. Ten of the 12 practices from Phase 2 received an emergency drill within 6 months of the original session. Three to four members of the whole team integrated training, attended the drill, but were unaware of the nature of the scenario before. Scoring was repeated and action plans were revisited to determine behaviour changes.ResultsEvery emergency drill demonstrated improved scoring in skills and behaviour.ConclusionA combination of: in situ GP simulation, appropriately qualified facilitators in simulation and debriefing, and action plans developed by the whole team suggests safer care for patients experiencing a medical emergency.

Clinical Drug Development for the Treatment of Pulmonary Arterial Hypertension: Collaboration With the Pharmaceutical Industry and Regulatory Agencies

2010 ◽  
Vol 9 (4) ◽  
pp. 214-219
Author(s):  
Robyn J. Barst
Keyword(s):  
Clinical Trials ◽  
Pulmonary Arterial Hypertension ◽  
Drug Development ◽  
Phase 1 ◽  
Preclinical Studies ◽  
Phase 2 ◽  
Phase 3 ◽  
Preclinical Testing ◽  
New Drug ◽  
Pulmonary Arterial

Drug development is the entire process of introducing a new drug to the market. It involves drug discovery, screening, preclinical testing, an Investigational New Drug (IND) application in the US or a Clinical Trial Application (CTA) in the EU, phase 1–3 clinical trials, a New Drug Application (NDA), Food and Drug Administration (FDA) review and approval, and postapproval studies required for continuing safety evaluation. Preclinical testing assesses safety and biologic activity, phase 1 determines safety and dosage, phase 2 evaluates efficacy and side effects, and phase 3 confirms efficacy and monitors adverse effects in a larger number of patients. Postapproval studies provide additional postmarketing data. On average, it takes 15 years from preclinical studies to regulatory approval by the FDA: about 3.5–6.5 years for preclinical, 1–1.5 years for phase 1, 2 years for phase 2, 3–3.5 years for phase 3, and 1.5–2.5 years for filing the NDA and completing the FDA review process. Of approximately 5000 compounds evaluated in preclinical studies, about 5 compounds enter clinical trials, and 1 compound is approved (Tufts Center for the Study of Drug Development, 2011). Most drug development programs include approximately 35–40 phase 1 studies, 15 phase 2 studies, and 3–5 pivotal trials with more than 5000 patients enrolled. Thus, to produce safe and effective drugs in a regulated environment is a highly complex process. Against this backdrop, what is the best way to develop drugs for pulmonary arterial hypertension (PAH), an orphan disease often rapidly fatal within several years of diagnosis and in which spontaneous regression does not occur?

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