How crowded is the cytoplasm?

Fulton, Alice

doi:10.1016/0092-8674(82)90231-8

Cited by 798 publications

(497 citation statements)

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“…Four values for the obstacle excluded volume have been considered: 0.031, 0.062, 0.124 and 0.187. We have chosen these densities in agreement with experimental data concerning to the range concentration of macromolecular crowding agents in cytoplasm, 0.05-0.4 [54][55]. We must underline that because of the repulsive interactions between the tracers, the total excluded volume of the system is the sum of φ plus the volume occupied by the tracers.…”

Section: Simulation Algorithmsupporting

confidence: 49%

Diffusion in macromolecular crowded media: Monte Carlo simulation of obstructed diffusion vs. FRAP experiments

et al. 2010

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Section: Simulation Algorithmsupporting

confidence: 49%

Diffusion in macromolecular crowded media: Monte Carlo simulation of obstructed diffusion vs. FRAP experiments

et al. 2010

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“…Next, we tested whether tau LLPS could occur at physiologically relevant tau concentrations, intracellular molecular crowding (≈50–400 mg/ml macromolecular density; Fulton, 1982), and electrolyte concentrations (≈100–200 mM; Lodish et al , 2000) conditions. The microscopic (i.e., visible in conventional light microscopy with a 63× objective) formation of p‐tau441 droplets could be observed at PEG concentrations ≥ 5% (≈crowding of ≥ 50 mg/ml macromolecule density without tau protein) and at a critical protein concentration of ≈1.0 μM (Fig 2G).…”

Section: Resultsmentioning

confidence: 99%

Tau protein liquid–liquid phase separation can initiate tau aggregation

et al. 2018

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The transition between soluble intrinsically disordered tau protein and aggregated tau in neurofibrillary tangles in Alzheimer's disease is unknown. Here, we propose that soluble tau species can undergo liquid–liquid phase separation (LLPS) under cellular conditions and that phase‐separated tau droplets can serve as an intermediate toward tau aggregate formation. We demonstrate that phosphorylated or mutant aggregation prone recombinant tau undergoes LLPS, as does high molecular weight soluble phospho‐tau isolated from human Alzheimer brain. Droplet‐like tau can also be observed in neurons and other cells. We found that tau droplets become gel‐like in minutes, and over days start to spontaneously form thioflavin‐S‐positive tau aggregates that are competent of seeding cellular tau aggregation. Since analogous LLPS observations have been made for FUS, hnRNPA1, and TDP43, which aggregate in the context of amyotrophic lateral sclerosis, we suggest that LLPS represents a biophysical process with a role in multiple different neurodegenerative diseases.

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“…Nevertheless, Sto$ hr et al (1993), De Marco et al (1994) and Meyerhoff et al (1994) proved the existence of pmNR by different approaches. The different efficiency of different buffer systems and, to some extent, the different findings of Hochman (1982) and the present study, may also be explained by the fact that cytosol is not just a bulk water system, but is rather a very concentrated solution and dense suspension with low water activities, thereby facilitating protein-protein interactions and interference by the numerous membranes (Fulton, 1982 ;cf. Howard & Solomonson, 1982).…”

Section: Soluble and Membrane-associated Nitrate Reductase In Peridinmentioning

confidence: 89%

Soluble and membrane‐associated nitrate reductases in the dinoflagellate Peridinium gatunense

1999

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An improved method of cell fractionation allowed the extraction of soluble (sNR) and membrane-associated (mNR) forms of nitrate reductase (NR) from a dinoflagellate, even though in previous studies only mNR had been found in these algae. Both activities were assayed in cell-free extracts of Peridinium gatunense from Lake Kinneret, Israel, after disruption of the cells and differential centrifugation. In the cultures used, sNR showed much higher NO $ − -reducing activity. Only a low proportion, 2n5-3% of NR activity, was found to be associated with mNR. Moreover, mNR comprised two forms as indicated by protein solubilization : a tightly membrane-bound and a more weakly attached NR. Ascorbate inhibited all NR activities, but that of mNR recovered after its removal. Polyvinyl pyrrolidone (PVP) and DTT also diminished sNR and mNR activities. For both enzymes, pH optima (7n65) and temperature optima (13-25mC) were similar, and agreed with those for optimum growth of P. gatunense both in culture and in the lake. The most efficient electron donor was NADH, though NADPH sustained low NR activities. Carboxylic anions such as succinate and malate did not support any reduction of NO $ − , nor did they cause any stimulation of sNR or mNR activities. Both forms of NR showed a high affinity for their substrates : K m was c. 10 µM for NO $ − and c. 5 µM for NADH. The high efficiency of NO $ − assimilation by Peridinium seems to be limited mainly by energy under otherwise optimal nutritional conditions and, at low nitrate concentrations, the low K m may be one of the main reasons for the high competitivity of this alga in Lake Kinneret.

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How crowded is the cytoplasm?

Cited by 798 publications

References 0 publications

Diffusion in macromolecular crowded media: Monte Carlo simulation of obstructed diffusion vs. FRAP experiments

Diffusion in macromolecular crowded media: Monte Carlo simulation of obstructed diffusion vs. FRAP experiments

Tau protein liquid–liquid phase separation can initiate tau aggregation

Soluble and membrane‐associated nitrate reductases in the dinoflagellate Peridinium gatunense

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