Polymerized LB films imaged with a combined atomic force microscope-fluorescence microscope

The first results obtained with a new stand-alone atomic force microscope (AFM) integrated with a standard Zeiss optical fluorescence microscope are presented. The optical microscope allows location and selection of objects to be imaged with the high-resolution AFM. Furthermore, the combined microscope enables a direct comparison between features observed in the fluorescence microscope and those observed in the images obtained with the AFM, in air or under liquid. The cracks in polymerized Langmuir-Blodgett films of lO,l2-pentacosadiynoic acid as observed in the fluorescence microscope run parallel to one of the lattice directions of the crystal as revealed by molecular resolution images obtained with the AFM. The orientation of these cracks also coincides with the polarization direction of the fluorescent light, indicating that the cracks run along the polymer backbone. Ripple-like corrugations on a submicrometer scale have been observed, which may be due to mechanical stress created during the polymerization process

Atomic Force Microscopy of DNA Electrophoresed onto Silylated Mica

A new technique has been developed for electrophoresing DNA molecules from an agarose gel onto a silylated mica substrate where they can be imaged with an atomic force microscope (AFM). With a simple modification, the technique can also be used for polyacrylamide gels. This method does not require purification of samples from the gels. Using tapping mode AFM, we have observed plasmids after electrophoretic separation into two bands. Differences in conformation were observed between the plasmids in the two bands

Improved Visualization of DNA in Aqueous Buffer with the Atomic Force Microscope

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 tips may be more damaging to DNA when imaged in aqueous buffer especially when the DNA is bound tightly to the mica. The ability to image DNA in nearly biological conditions has potential applications for imaging biomolecular processes with the AFM

Mechanical Energy before Chemical Energy at the Origins of Life?

Mechanical forces and mechanical energy are prevalent in living cells. This may be because mechanical forces and mechanical energy preceded chemical energy at life’s origins. Mechanical energy is more readily available in nonliving systems than the various forms of chemical energy used by living systems. Two possible prebiotic environments that might have provided mechanical energy are hot pools that experience wet/dry cycles and mica sheets as they move, open and shut, as heat pumps or in response to water movements

Correction: Hansma, H.G. Potassium at the Origins of Life: Did Biology Emerge from Biotite in Micaceous Clay? Life 2022, 12, 301

The author wishes to make the following correction to this paper [...

Could Life Originate between Mica Sheets?: Mechanochemical Biomolecular Synthesis and the Origins of Life

ABSTRACT The materials properties of mica have surprising similarities to those of living systems. The mica hypothesis is that life could have originated between mica sheets, which provide stable compartments, mechanical energy for bond formation, and the isolation needed for Darwinian evolution. Mechanical energy is produced by the movement of mica sheets, in response to forces such as ocean currents or temperature changes. The energy of a carbon-carbon bond at room temperature is comparable to a mechanical force of 6 nanoNewtons (nN) moving a distance of 100 picometers. Mica's movements may have facilitated mechanochemistry, resulting in the synthesis of prebiotic organic molecules. Furthermore, mica's movements may have facilitated the earliest cell divisions, at a later stage of life's origins. Mica's movements, pressing on lipid vesicles containing proto-cellular macromolecules, might have facilitated the blebbing off of 'daughter' protocells. This blebbing-off process has been observed recently in wall-less L-form bacteria and is proposed to be a remnant of the earliest cell divisions (Leaver, et al. Nature 457, 849 (2009)

Better than Membranes at the Origin of Life?

Organelles without membranes are found in all types of cells and typically contain RNA and protein. RNA and protein are the constituents of ribosomes, one of the most ancient cellular structures. It is reasonable to propose that organelles without membranes preceded protocells and other membrane-bound structures at the origins of life. Such membraneless organelles would be well sheltered in the spaces between mica sheets, which have many advantages as a site for the origins of life

Potassium at the Origins of Life: Did Biology Emerge from Biotite in Micaceous Clay?

Intracellular potassium concentrations, [K+], are high in all types of living cells, but the origins of this K+ are unknown. The simplest hypothesis is that life emerged in an environment that was high in K+. One such environment is the spaces between the sheets of the clay mineral mica. The best mica for life’s origins is the black mica, biotite, because it has a high content of Mg++ and because it has iron in various oxidation states. Life also has many of the characteristics of the environment between mica sheets, giving further support for the possibility that mica was the substrate on and within which life emerged. Here, a scenario for life’s origins is presented, in which the necessary processes and components for life arise in niches between mica sheets; vesicle membranes encapsulate these processes and components; the resulting vesicles fuse, forming protocells; and eventually, all of the necessary components and processes are encapsulated within individual cells, some of which survive to seed the early Earth with life. This paper presents three new foci for the hypothesis of life’s origins between mica sheets: (1) that potassium is essential for life’s origins on Earth; (2) that biotite mica has advantages over muscovite mica; and (3) that micaceous clay is a better environment than isolated mica for life’s origins