PENERAPAN PEMBELAJARAN KOOPERATIF PDEODE DENGAN BANTUAN SIMULASI KOMPUTER UNTUK MENGURANGI MISKONSEPSI SISWA SMA PADA MATERI LISTRIK DINAMIS

Berdasarkan studi literatur, cukup banyak siswa yang mengalami miskonsepsi. Miskonsepsi merupakan pemahaman suatu konsep yang diyakini secara kuat namun konsep yang diyakini tidak sesuai dengan konsep-konsep ilmiah para ahli. Miskonsepsi apabila tidak diperbaiki akan memahami salah konsep selamanya. Sehingga, miskonsepsi dipandang penting untuk diubah agar siswa memiliki pemahaman konsep yang benar. Untuk mengatasi miskonsepsi diperlukan pembelajaran yang mampu membuat siswa menggali konsep sendiri, dalam hal ini peneliti menggunakan pembelajaran kooperatif PDEODE menggunakan simulasi komputer . Tujuan penelitian ini adalah untuk melihat penerapan pembelajaran PDEODE dengan bantuan simulasi komputer dapat mengurangi miskonsepsi siswa pada materi listrik dinamis. Penelitian ini menggunakan metode quasi experiment jenis Pre test and Post test Group Design dengan sampel 27 siswa pada salah satu SMA Boarding di Kabupaten Bandung Barat secara purposive sample. Hasil penelitian mengungkapkan bahwa pembelajaran kooperatif PDEODE dapat menurunkan miskonsepsi siswa.;---Based on study of some literature, there are students who have misconceptions. The misconception is understanding a concept that is believed to be strong but inconsistent with the concepts of scientis. If it’s not corrected, student wouldn’t be understand on concept forever. Therefore, misconceptions is essential to be changed until they have true concepts. Cooperative learning PDEODE with computer simulations was used to overcome misconceptions required learning that makes the students explore own concept. The purpose of this study is to look at the application of cooperative learning PDEODE with the support of computer simulations can reduce misconceptions students on the dynamic electricity. This study uses quasi experimental test types Pre and Post Test Group Design with a sample of 27 students at one high school in West Bandung. Results of the study revealed that cooperative learning PDEODE can reduce misconceptions students

pH-dependent interactions of coacervate-forming histidine-rich peptide with model lipid membranes

Peptide-based liquid droplets (coacervates) produced by spontaneous liquid-liquid phase separation (LLPS), have emerged as a promising class of drug delivery systems due to their high entrapping efficiency and the simplicity of their formulation. However, the detailed mechanisms governing their interaction with cell membranes and cellular uptake remain poorly understood. In this study, we investigated the interactions of peptide coacervates composed of HBpep—peptide derived from the histidine-rich beak proteins (HBPs) of the Humboldt squid—with model cellular membranes in the form of supported lipid bilayers (SLBs). We employed quartz crystal microbalance with dissipation monitoring (QCM-D), neutron reflectometry (NR) and atomistic molecular dynamics (MD) simulations to reveal the nature of these interactions in the absence of fluorescent labels or tags. HBpep forms small oligomers at pH 6 whereas it forms µm-sized coacervates at physiological pH. Our findings reveal that both HBpep oligomers and HBpep-coacervates adsorb onto SLBs at pH 6 and 7.4, respectively. At pH 6, when the peptide carries a net positive charge, HBpep oligomers insert into the SLB, facilitated by the peptide’s interactions with the charged lipids and cholesterol. Importantly, however, HBpep coacervate adsorption at physiological pH, when it is largely uncharged, is fully reversible, suggesting no significant lipid bilayer rearrangement. HBpep coacervates, previously identified as efficient drug delivery vehicles, do not interact with the lipid membrane in the same manner as traditional cationic drug delivery systems or cell-penetrating peptides. Based on our findings, HBpep coacervates at physiological pH cannot cross the cell membrane by a simple passive mechanism and are thus likely to adopt a non-canonical cell entry pathway

Structure of Lipoproteins and Their Capacity for Lipid Exchange: Relevance for Development of Atherosclerosis and Its Treatment by HDL Therapy

Atherosclerosis, the largest killer in the western world, arises from build-up of plaques at the artery walls and can result in cardiovascular disease. Low- and high-density lipoproteins are involved in the disease development by depositing and removing lipids to and from macrophages at the artery wall. These processes are complex and not fully understood. Thus, determining the specific roles of the different lipoprotein fractions involved is of fundamental importance for the treatment of the disease. In this chapter, we present the state of the art in lipoprotein structure with focus on the comparison between normolipidemic and hypertriglyceridemic individuals. Then we discuss lipid transfer between lipoproteins and receptor-free cellular membranes. Although these models lack any receptor, key clinical observations are mirrored by these, including increased ability of HDL to remove lipids, in contrast to the ability of LDL to deposit them. Also effects of saturated and unsaturated lipids in the presence and absence of cholesterol are revised. These models can then be used to understand the difference in functionality of lipoproteins from individuals showing different lipid profiles and have the potential to be used also for the development of new HDL therapies

Biophysical study of resin acid effects on phospholipid membrane 1 structure and properties

Hydrophobic resin acids (RAs) are synthesized by conifer trees as part of their defense mechanisms. One of the functions of RAs in plant defense is suggested to be the perturbation of the cellular membrane. However, there is a vast diversity of chemical structures within this class of molecules, and there are no clear correlations to the molecular mechanisms behind the RA's toxicity. In this study we unravel the molecular interactions of the three closely related RAs dehydroabietic acid, neoabietic acid, and the synthetic analogue dichlorodehydroabietic acid with dipalmitoylphosphatidylcholine (DPPC) model membranes and the polar lipid extract of soybeans. The complementarity of the biophysical techniques used (NMR, DLS, NR, DSC, Cryo-TEM) allowed correlating changes at the vesicle level with changes at the molecular level and the co-localization of RAs within DPPC monolayer. Effects on DPPC membranes are correlated with the physical chemical properties of the RA and their toxicity

Continuous Flow AFM Imaging Reveals Fluidity and Time Dependent Interactions of Antimicrobial Dendrimer with Model Lipid Membranes

In this paper, an amphiphilic peptide dendrimer with potential applications against multi-resistant bacteria such as Staphylococcus aureus was synthesized and studied on model cell membranes. The combination of quartz crystal microbalance and atomic force microscopy imaging during continuous flow allowed for in situ monitoring of the very initial interaction processes and membrane transformations on longer time scales. We used three different membrane compositions of low and high melting temperature phospholipids to vary the membrane properties from a single fluid phase to a pure gel phase, while crossing the phase coexistence boundaries at room temperature. The interaction mechanism of the dendrimer was found to be time-dependent and to vary remarkably with the fluidity and coexistence of liquid-solid phases in the membrane. Spherical micelle-like dendrimer-lipid aggregates were formed in the fluid-phase bilayer and led to partial solubilization of the membrane, while in gel-phase membranes, the dendrimers caused areas of local depressions followed by redeposition of flexible lipid patches. Domain coexistence led to a sequence of events initiated by the formation of a ribbon-like network and followed by membrane solubilization via spherical aggregates from the edges of bilayer patches. Our results show that the dendrimer molecules were able to destroy the membrane integrity through different mechanisms depending on the lipid phase and morphology and shed light on their antimicrobial activity. These findings could have an impact on the efficacy of the dendrimers since lipid membranes in certain bacteria have transition temperatures very close to the host body temperature

Review of structural design guiding the development of lipid nanoparticles for nucleic acid delivery

Lipid nanoparticles (LNPs) are the most versatile and successful gene delivery systems, notably highlighted by their use in vaccines against COVID-19. LNPs have a well-defined core-shell structure, each region with its own distinctive compositions, suited for a wide range of in vivo delivery applications. Here, we discuss how a detailed knowledge of LNP structure can guide LNP formulation to improve the efficiency of delivery of their nucleic acid payload. Perspectives are detailed on how LNP structural design can guide more efficient nucleic acid transfection. Views on key physical characterization techniques needed for such developments are outlined including opinions on biophysical approaches both correlating structure with functionality in biological fluids and improving their ability to escape the endosome and deliver they payload

Neutron reflectometry to investigate the delivery of lipids and DNA to interfaces (Review)

The application of scattering methods in the study of biological and biomedical problems is a field of research that is currently experiencing fast growth. In particular, neutron reflectometry (NR) is a technique that is becoming progressively more widespread, as indicated by the current commissioning of several new reflectometers worldwide. NR is valuable for the characterization of biomolecules at interfaces due to its capability to provide quantitative structural and compositional information on relevant molecular length scales. Recent years have seen an increasing number of applications of NR to problems related to drug and gene delivery. We start our review by summarizing the experimental methodology of the technique with reference to the description of biological liquid interfaces. Various methods for the interpretation of data are then discussed, including a new approach based on the lattice mean-field theory to help characterize stimulus-responsive surfaces relevant to drug delivery function. Recent progress in the subject area is reviewed in terms of NR studies relevant to the delivery of lipids and DNA to surfaces. Lastly, we discuss two case studies to exemplify practical features of NR that are exploited in combination with complementary techniques. The first case concerns the interactions of lipid-based cubic phase nanoparticles with model membranes (a drug delivery application), and the second case concerns DNA compaction at surfaces and in the bulk solution (a gene delivery application). (C) 2008 American Vacuum Society. [DOI: 10.1116/1.2976448

Influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb(II) ion-selective electrode

In this work, the influence of phosphate buffer and proteins on the potentiometric response of a polymeric membrane-based solid-contact Pb2+-selective electrode (Pb2+-ISE) was studied. The effects of bovine serum albumin (BSA) adsorption at the surface of the ion-selective membrane combined with electrode conditioning in phosphate-buffered saline (PBS) solution was elucidated by potentiometry and electrochemical impedance spectroscopy. The adsorbed BSA at the surface of the Pb2+-ISE slightly lowered the detection limit but did not influence the selectivity of the Pb2+-ISE towards the interfering ions studied (Cu2+, Cd2+). Conditioning of the Pb2+-ISE in 0.01 mol dm–3 PBS resulted in a super-Nernstian response which was related to fixation/extraction of Pb2+ in the ion-selective membrane via precipitation of Pb3(PO4)2 by PO43– anions present in PBS. By conditioning of the Pb2+-ISE in 0.01 mol dm–3 PBS + 1 mg/ml BSA it was possible to extend the linear response range of the Pb2+-ISE towards lower analyte concentrations. The utilization of this conditioning procedure was validated by determination of Pb2+ concentrations down to ca 20 ppb in aqueous samples by Pb2+-ISEs and by comparing the results with those obtained by ICP-MS

Towards biomimics of cell membranes: Structural effect of phosphatidylinositol triphosphate (PIP3) on a lipid bilayer

Phosphoinositide (PIP) lipids are anionic phospholipids playing a fundamental role for the activity of several transmembrane and soluble proteins. Among all, phosphoinositol-3',4',5'-trisphosphate (PIP3) is a secondary signaling messenger that regulates the function of proteins involved in cell growth and gene transcription. The present study aims to reveal the structure of PIP-containing lipid membranes, which so far has been little explored. For this purpose, supported lipid bilayers (SLBs) containing 1,2-dioleoyl-sn-glycero-3-phospho-(1'-myoinositol-3',4',5'-trisphosphate (DOPIP3) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were used as mimics of biomembranes. Surface sensitive techniques, i.e. Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), Atomic Force Microscopy (AFM) and Neutron Reflectometry (NR), provided detailed information on the formation of SLB and the location of DOPIP3 in the lipid membrane. Specifically, QCMD and AFM were used to identify the best condition for lipid deposition and to estimate the total bilayer thickness. On the other hand, NR was used to collect experimental structural data on the DOPIP3 location and orientation within the lipid membrane. The two bilayer leaflets showed the same DOPIP3 concentration, thus suggesting the formation of a symmetric bilayer. The headgroup layer thicknesses of the pure POPC and the mixed POPC/DOPIP3 bilayer suggest that the DOPIP3-headgroups have a preferred orientation , which is not perpendicular to the membrane surface, but instead it is close to the surrounding lipid headgroups. These results support the proposed PIP3 tendency to interact with the other lipid headgroups as PC, so far exclusively suggested by MD simulations