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Full-Text Articles in Life Sciences
Contact Force Dependence On Relative Humidity: Investigations Using Atomic Force Microscopy, E. Finot, E. Lesniewska, J. -C. Mutin, S. I. Hosain, J. -P. Goudonnet
Contact Force Dependence On Relative Humidity: Investigations Using Atomic Force Microscopy, E. Finot, E. Lesniewska, J. -C. Mutin, S. I. Hosain, J. -P. Goudonnet
Scanning Microscopy
This paper deals with the ability of scanning force microscopy to determine contact forces of various materials. Indeed, with high spring constants at low relative humidity, the nature of the material can be determined by measurement of the contact force as the tip approaches. Cantilevers with a high spring constant are used to achieve solid-solid contact for the tip-sample system. The capillary force estimation provides information on the development of the height of the water meniscus formed between the tip and different surfaces depending on the relative humidity. Finally, we focus our attention on measurements of moduli of elasticity which …
Improved Visualization Of Dna In Aqueous Buffer With The Atomic Force Microscope, Magdalena Bezanilla, Carlos J. Bustamante, Helen G. Hansma
Improved Visualization Of Dna In Aqueous Buffer With The Atomic Force Microscope, Magdalena Bezanilla, Carlos J. Bustamante, Helen G. Hansma
Scanning Microscopy
An improved method has been developed for imaging deoxyribonucleic acid (DNA) in aqueous buffer with the atomic force microscope (AFM). DNA on untreated mica can be imaged in aqueous buffer with the AFM if the DNA is deposited onto the mica in a buffer with HEPES and MgCl2, if the sample is rinsed thoroughly with high water pressure, and if the imaging is done with an electron beam-deposited (EBD) tip that has been deposited in the scanning electron microscope (SEM). The water rinse removes DNA that is otherwise easily scraped off the substrate. There is evidence that sharper …
Can We See Living Structure In A Cell?, Gilbert N. Ling
Can We See Living Structure In A Cell?, Gilbert N. Ling
Scanning Microscopy
Colloid chemistry (κολλα: glue, or gelatin) was introduced in 1861 after the discovery of protoplasm which exhibits gelatin-like properties. Some 80 years later, colloid chemistry (and with it, the concept of protoplasm) was largely abandoned. The membrane (pump) theory, according to which cell water and cell solute like K+ are free as in a dilute KCl solution, became dominant. Later studies revealed that rejecting the protoplasmic approach to cell physiology was not justified. Evidence against the membrane (pump) theory, on the other hand, has stood the test of time. In a new theory of the living cell called the …
Diffusion Of Water In Biological Tissues, H. E. Rorschach, C. Lin, C. F. Hazlewood
Diffusion Of Water In Biological Tissues, H. E. Rorschach, C. Lin, C. F. Hazlewood
Scanning Microscopy
A method is presented for obtaining simple approximate solutions for the problem of self-diffusion in an ordered array of obstacles. Our results are compared with some previous exact and approximate solutions, and we find that our method agrees well with the exact results over a large range of the volume fraction of the obstructions. It is shown that there is an important distinction between measurements of the diffusion coefficient by the capillary flow method and the spin-echo method. The modifications for the spin-echo case are given and applied to recent measurements on the anisotropy of the self-diffusion of water in …
The Hall Method In The Quantitative X-Ray Microanalysis Of Biological Specimens: A Review, Godfried M. Roomans
The Hall Method In The Quantitative X-Ray Microanalysis Of Biological Specimens: A Review, Godfried M. Roomans
Scanning Microscopy
In the two decades since its inception by T.A. Hall, the continuum theory of quantification has become the general method for quantitative analysis of biological specimens. Although the method was originally developed for thin specimens, its use has been extended to thicker specimens, and it has also been used in quantitative determinations of local water content. The single most important difficulty in the application of the "Hall method" is the accurate calculation of the extraneous continuum, i.e., the continuum due to non-specimen sources. The different variations in methods for quantitative analysis of local water content are critically compared and a …
The Physical State Of Potassium Ion In The Living Cell, G. N. Ling
The Physical State Of Potassium Ion In The Living Cell, G. N. Ling
Scanning Microscopy
This review summarizes more than 30 years of experimental testing (and confirmation) of a key postulate of the association-induction (AI) hypothesis: most K+ ions in resting cells are adsorbed on 𝛃-and 𝛄-carboxyl group of cell proteins in a close-contact one ion-one site manner. Failure of healthy, cytoplasm-free, squid axon-membrane sacs to selectively accumulate K+ over Na+ and success of muscle cells without a functional cell membrane (and postulated pumps) to achieve the same, point to the cytoplasm as the seat of selective K+ accumulation. Four independent techniques unanimously confirmed the predicted localization in striated muscle cells, …
A Physical Theory Of The Living State: Application To Water And Solute Distribution, G. N. Ling
A Physical Theory Of The Living State: Application To Water And Solute Distribution, G. N. Ling
Scanning Microscopy
This review begins with a summary of the disproof of the membrane-pump theory and the alternative theory of the living cell, the association-induction (AI) hypothesis. Being alive in the AI hypothesis represents the maintenance of a high (negative) energy-low entropy state in which the two major components K+ and water of the living cell are closely associated with the third major component of the living cells, proteins. K+ is adsorbed singly on 𝜷-and γ-carboxyl groups and the bulk of cell water in multilayers on the exposed NHCO groups of fully extended polypeptide chains of cell proteins. These adsorptions …
Overview Of Physical Studies Of Bulk Water In Biopolymers, Wm. Negendank
Overview Of Physical Studies Of Bulk Water In Biopolymers, Wm. Negendank
Scanning Microscopy
The Symposium of which this paper is a part, "The State Of Water In The Cell", examines evidence which indicates that the bulk water of the cell has physical properties that are different from those of free water in a dilute aqueous solution. The heterogeneity of environments of water within cells makes direct application of physical studies difficult. However, the major physiologic effect of an ordered state of bulk cell water is solute exclusion, and this is also demonstrated by simple polymer solutions. Such systems have provided an opportunity to show that such water has motional correlation times within an …
Ion And Water Retention By Permeabilized Cells, Carlton F. Hazlewood, Miklos Kellermayer
Ion And Water Retention By Permeabilized Cells, Carlton F. Hazlewood, Miklos Kellermayer
Scanning Microscopy
Nonionic detergents, Triton X-100 and Brij 58, removed, within 2-5 minutes, lipid membrane of suspended thymus lymphocytes and monolayer H-50 cells grown in culture. Studies of hydration, ionic asymmetry, and ionic and protein release kinetics were conducted on these membraneless cellular preparations. The hydration of nuclei isolated by Triton X-100 procedures appears to be influenced strongly by the monovalent ionic concentration of the buffer bathing the organelles. The putative monovalent ionic concentration of the cellular aqueous phase (i.e., 150 meq/L) caused nuclei to swell and coalesce. Monovalent ionic concentrations of 30 meq/L or less caused minimal changes in volume and …
Quasi-Elastic Scattering Studies Of Water Diffusion, H. E. Rorschach, D. W. Bearden, C. F. Hazlewood, D. B. Heidorn, R. M. Nicklow
Quasi-Elastic Scattering Studies Of Water Diffusion, H. E. Rorschach, D. W. Bearden, C. F. Hazlewood, D. B. Heidorn, R. M. Nicklow
Scanning Microscopy
Quasi-elastic neutron scattering is a powerful method to study the dynamics of protons in biological systems. The technique has been used both for the study of water diffusion and protein motion. The neutron scattering measurements on water show that the translational and rotational diffusion coefficients in biological systems are reduced from bulk values. We review the measurements on water in frog muscle, cysts of artemia, and phycocyanin. Measurements on dry trypsin and trypsin-D2O solutions over the temperature range 75-300K show that there is proton motion at the one angstrom level even in the dry or frozen state.