Molecular Sieves
Molecular Sieves - Related Videos
01:19
Sieve Analysis and Grading Curves
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2024
Sieve analysis is a method used to determine the particle size distribution of aggregate materials. This process involves the following steps: The required quantity of dried sample of aggregate is weighed. The weighed aggregates are sieved through a set of sieves with square openings arranged in descending order of aperture size, with the largest mesh on top (Column 1 of Table 1). The stack of sieves is shaken or vibrated to facilitate the sorting of particles by size. After sieving for a...
14:16
A New Application of the Electrical Penetration Graph (EPG) for Acquiring and Measuring Electrical Signals in Phloem Sieve Elements
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Cited by 24 •
2015
Electrical Penetration Graph (EPG) is a well-established technique for studying the feeding behavior of stylet-bearing insects. Here we show a new application of EPG as a non-invasive tool for the acquisition of intracellular electrophysiology recordings of sieve elements (SEs), the cells that form the phloem vasculature in plants.
09:55
Molecular Cloning
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2023
Molecular cloning is a set of methods, which are used to insert recombinant DNA into a vector - a carrier of DNA molecules that will replicate recombinant DNA fragments in host organisms. The DNA fragment, which may be a gene, can be isolated from a prokaryotic or eukaryotic specimen. Following isolation of the fragment of interest, or insert, both the vector and insert must be cut with restriction enzymes and purified. The purified pieces are joined together though a technique called...
12:02
Molecular Evolution of the Tre Recombinase
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Cited by 4 •
2008
Here we report the generation of Tre recombinase through directed, molecular evolution. Tre recombinase recognizes a pre-defined target sequence within the LTR sequences of the HIV-1 provirus, resulting in the excision and eradication of the provirus from infected human cells. While still in its infancy, directed molecular evolution will allow the creation of custom enzymes that will serve as tools of molecular surgery and molecular medicine.
04:39
Caenorhabditis Sieve: A Low-tech Instrument and Methodology for Sorting Small Multicellular Organisms
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Cited by 5 •
2018
The current protocol includes a methodology for the sorting and cleaning of age-matched populations of Caenorhabditis elegans. It uses a simple, inexpensive, and efficient custom-made tool to obtain a large experimental population of nematodes for research.
FAQs
Separation depends on whether a molecule can enter the sieve’s uniform channels and cavities. Smaller molecules may access internal surfaces, whereas larger or poorly shaped molecules are excluded. Polarity also influences adsorption, so molecules of similar size may interact differently with the material. This combination of size, shape, and polarity gives molecular sieves their selective behavior.
Polarity changes how strongly a molecule interacts with the internal surfaces of the sieve. Consequently, molecules that fit the pores are not necessarily retained to the same extent. Considering polarity alongside molecular dimensions helps explain selective adsorption and allows chemists to distinguish compounds that might otherwise have similar access to the channels and cavities.
Adsorbed molecules can be released by heating the material or reducing the pressure. This reversibility allows the sieve to be regenerated rather than treated as a permanently consumed reagent. In practice, the same material can support repeated drying or separation operations, while controlled release also helps recover substances held on its internal surfaces.
Their pore structures can regulate which molecules reach catalytic active sites. Molecules that enter the channels may contact those sites, while larger molecules can be excluded, changing the reaction environment within the material. This size-selective access can support selective synthesis by limiting competing interactions and concentrating the relevant molecular components near catalytic regions.
Chemists place the porous material in contact with a solvent or gas so trace water can be adsorbed on its internal surfaces. Because adsorption is selective and reversible, the sieve can remove residual moisture and later be regenerated through heating or pressure reduction. This supports preparation of drier chemical streams for subsequent laboratory or process use.
They are useful when mixture components differ in size, shape, or polarity and can therefore interact differently with the sieve’s pores. The material may admit some molecules while excluding others, producing selective retention. Researchers can apply this principle to purification, solvent or gas treatment, and chemical synthesis where controlling composition improves the desired outcome.