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- نموذج دافسون ودانيلي كان نموذج للغشاء الخلوي صممه كل من العالمين دافسون(Hugh Davson) ودانيلي (James Danielli) في عام 1935. يصف هذا النموذج الغشاء الخلوي على أنه مؤلف من ليبيد ثنائي الطبقة وأن كلا سطحي هذه الطبقة مغطى بالبروتينات الكُرَيْوِيّة، والتي تُغطي السحطين الخارجيين لهذه الطبقة فقط من غير أن تمتد عبرها أو تنغرس فيها. (ar)
- The Davson–Danielli model (or paucimolecular model) was a model of the plasma membrane of a cell, proposed in 1935 by Hugh Davson and James Danielli. The model describes a phospholipid bilayer that lies between two layers of globular proteins, which is both trilaminar and lipoprotinious. The phospholipid bilayer had already been proposed by Gorter and Grendel in 1925; however, the flanking proteinaceous layers in the Davson–Danielli model were novel and intended to explain Danielli's observations on the surface tension of lipid bilayers (It is now known that the phospholipid head groups are sufficient to explain the measured surface tension). Evidence for the model included electron microscopy, in which high-resolution micrographs showed three distinct layers within a cell membrane, with an inner white core and two flanking dark layers. Since proteins usually appear dark and phospholipids white, the micrographs were interpreted as a phospholipid bilayer sandwiched between two protein layers. The model proposed an explanation for why certain substances were not able to pass through cell membranes, while also accounting for the thinness of membranes. Despite the Davson–Danielli model being scientifically accepted, the model made assumptions, and couldn't account for observed phenomena. For example, the model assumed that all membranes had the same structure, which couldn't explain how different types of membranes could have different functions. Another shortcoming of the Davson–Danielli model is that proteins, while amphipathic, are mostly hydrophobic, so the existence of proteins on the outside of the cell membranes in direct contact with water presented an issue. The Davson–Danielli model was scientifically accepted until Seymour Jonathan Singer and Garth L. Nicolson advanced the fluid mosaic model in 1972. The fluid mosaic model expanded on the Davson–Danielli model by including transmembrane proteins, and eliminated the previously-proposed flanking protein layers that were not well-supported by experimental evidence. The experimental evidence that falsified the Davson–Danielli model included membrane freeze-fracturing, which revealed irregular rough surfaces in the membrane and fluorescent antibody tagging of membrane proteins, which demonstrated their fluidity within the membrane. (en)
- Il modello di unità di membrana (o modello di Davson-Danielli) è un'ipotesi descrittiva della membrana cellulare. Il "modello di unità di membrana" La prima indicazione che i lipidi delle membrane biologiche sono organizzati in un doppio strato risale al 1925, quando Garter e Grendel dimostrarono che i lipidi estratti con acetone dalla membrana plasmatica dei globuli rossi (l'unica membrana presente negli eritrociti) occupavano una superficie doppia rispetto a quella dell'intera cellula. Il modello di membrana cellulare proposto da Danielli e Davson del 1935, poi ripreso da Robertson nel 1959, è conosciuto come "modello di unità di membrana". Secondo questo modello la membrana cellulare avrebbe una struttura trilaminare di circa 75 Å di spessore, con due strati esterni di natura proteica con configurazione beta ed uno strato intermedio lipidico, come risultava dalle caratteristiche immagini "a binario ferroviario" osservate al microscopio elettronico. Questo aspetto trilaminare, dovuto alla fissazione con tetrossido di osmio o permanganato di potassio, consisteva infatti in due strati periferici densi agli elettroni di 15 Å e uno strato intermedio di 40 Å trasparente agli elettroni. (it)
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- نموذج دافسون ودانيلي كان نموذج للغشاء الخلوي صممه كل من العالمين دافسون(Hugh Davson) ودانيلي (James Danielli) في عام 1935. يصف هذا النموذج الغشاء الخلوي على أنه مؤلف من ليبيد ثنائي الطبقة وأن كلا سطحي هذه الطبقة مغطى بالبروتينات الكُرَيْوِيّة، والتي تُغطي السحطين الخارجيين لهذه الطبقة فقط من غير أن تمتد عبرها أو تنغرس فيها. (ar)
- The Davson–Danielli model (or paucimolecular model) was a model of the plasma membrane of a cell, proposed in 1935 by Hugh Davson and James Danielli. The model describes a phospholipid bilayer that lies between two layers of globular proteins, which is both trilaminar and lipoprotinious. The phospholipid bilayer had already been proposed by Gorter and Grendel in 1925; however, the flanking proteinaceous layers in the Davson–Danielli model were novel and intended to explain Danielli's observations on the surface tension of lipid bilayers (It is now known that the phospholipid head groups are sufficient to explain the measured surface tension). (en)
- Il modello di unità di membrana (o modello di Davson-Danielli) è un'ipotesi descrittiva della membrana cellulare. Il "modello di unità di membrana" La prima indicazione che i lipidi delle membrane biologiche sono organizzati in un doppio strato risale al 1925, quando Garter e Grendel dimostrarono che i lipidi estratti con acetone dalla membrana plasmatica dei globuli rossi (l'unica membrana presente negli eritrociti) occupavano una superficie doppia rispetto a quella dell'intera cellula. (it)
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- نموذج دافسون ودانيلي (ar)
- Davson–Danielli model (en)
- Modello di unità di membrana (it)
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