Molecular Structure of Biological Membranes: Functional Characterization

Malhotra, S. K.

doi:10.1007/978-1-4615-7942-7_5

Cited by 3 publications

(2 citation statements)

References 128 publications

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“…It is conceivable that such fractured faces represent regions of the membrane that are deficient in particles. Alternatively, they may represent insjde-out vesicles and the two fractured faces show an asymmetric distribution of intramembranous particles, there being a few on one half [22].…”

Section: Jss: 331mentioning

confidence: 99%

β‐Bungarotoxin binding sites (acetylcholine receptors) in denervated mammalian sarcolemma

Tipnis

Malhotra

1979

J Supramol Struct

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The nonsynaptic sarcolemma of denervated skeletal muscle of rat shows an abundance of approximately 15 nm intramembranous particles on the P face. These particles are either singly distributed or are in clusters, and they are essentialy lacking from the comparable freeze-fractures of the innervated sarcolemma. Autoradiographic studies using 125I-alpha-bungarotoxin (BGT) on 1 mu-thick sections, and freeze-etch studies using ferritin-alpha-BGT conjugates on membrane fractions, show that the distribution of the label corresponds to the distribution of the 15-nm particles in the nonsynaptic sarcolemma. On the basis of these results and existing physiologic and biochemical data, it is suggested that the 15-nm intramembranous particles are components of the alpha-BGT binding sites, ie, acetylcholine (Ach) receptors, in the nonsynaptic sarcolemma of denervated muscle and that the two types of distributions represent two spatial manifestations of Ach receptor molecules. The significance of these findings in relation to synapse formation in denervated muscle is discussed.

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Section: Jss: 331mentioning

confidence: 99%

β‐Bungarotoxin binding sites (acetylcholine receptors) in denervated mammalian sarcolemma

Tipnis

Malhotra

1979

J Supramol Struct

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“…The sporangia of this fungus represent the repeating progapule stage (1). P. blakesleeanus is a saprophytic fungus and has been extensively studied to elucidate the mechanism of photoreception and other behavioral responses (3, 8,10,20).…”

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confidence: 99%

Multilamellar surface layer of the cell wall of Albugo candida and Phycomyces blakesleeanus

Tewari¹,

Skoropad²,

Malhotra³

1980

J Bacteriol

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The surface layer of the cell wall of the sporangia of Albugo candida and of the sporangiophores of Phycomyces blakesleeanus was composed of a series of lamellae. The evidence from freeze-fracture, freeze-etch, and single-stage replicas indicated that the lamellae are organized as bilayers, an organization associated with the presence of lipids. The role of these lamellae in dispersibility and resistance is discussed.Surface characteristics of the propagules of fungi may play a role(s) in their dispersibility and resistance to desiccation. In many fungi these roles have been attributed to the presence of a layer consisting of rodlets on the surface of spores (2). The rodlets are not unique to spores since they are also present on the surface of the hyphae of wild-type Neurospora crassa (Tewari and Malhotra, unpublished data) where they may serve to protect the hyphae against desiccation.During an investigation of phycomycetous fungi (Albugo candida and Phycomyces blakesleeanus), it was observed that the surface layer of these fungi had characteristic lamellar organization, usually associated with the presence of lipids. Such a structure, although suited for protection against desiccation, does not appear to have been reported in the available literature. Consequently, the structure of this surface layer in the two fungi is reported in the present paper with a view toward understanding the structure and chemical nature of their surface layer. A. candida is an obligate parasite ofthe cruciferous plants and causes heavy economic loss all over the world. The sporangia of this fungus represent the repeating progapule stage (1). P. blakesleeanus is a saprophytic fungus and has been extensively studied to elucidate the mechanism of photoreception and other behavioral responses (3,8,10,20). MATERLALS AND METHODSMature leaves of the Polish rapeseed cultivar Torch (Brassica campestris) infected with A. candida were collected from the University of Alberta Farm in Edmonton, Alberta. Cultures of P. blakesleeanus were grown in glucose-asparagine agar (22) in petri dishes kept in moist chambers under constant fluorescent light at room temperature (-22°C).The sporangia of A. candida and the sporangiophores of P. blakesleeanus (stage IV; see reference 3) were fixed overnight in a 1:1 mixture of 3% glutaraldehyde and 3% formaldehyde in 0.1 M phosphate buffer (pH 7). They were then soaked in 25% glycerol in water for 30 min, placed on Au-Ni specimen holders, frozen in Freon 22, and stored in liquid nitrogen. Unidirectionally shadowed platinum-carbon replicas of the materials fractured at -100°C were made in a Balzers BA 360M high-vacuum freeze-etch unit, using standard techniques (11,18).For making replicas of the freeze-etched specimens, materials fixed in the aldehyde mixture were washed in distilled water for 2 h and processed as described above except that the fractured material was etched for 1.5 min at -100°C.Pt-C replicas of the surface of the two materials were prepared as follows. A thin layer of Tissue-Tek (an embedding ...

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Macromolecular Organization of the Nicotinic Acetylcholine Receptors

Malhotra

1981

Subcellular Biochemistry

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Molecular Structure of Biological Membranes: Functional Characterization

Cited by 3 publications

References 128 publications

β‐Bungarotoxin binding sites (acetylcholine receptors) in denervated mammalian sarcolemma

β‐Bungarotoxin binding sites (acetylcholine receptors) in denervated mammalian sarcolemma

Multilamellar surface layer of the cell wall of Albugo candida and Phycomyces blakesleeanus

Macromolecular Organization of the Nicotinic Acetylcholine Receptors

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