Non-chaotropic chemistry

Non-Chaotropic Chemistry - Unique and proprietary core technology

The development of non-chaotropic chemistry by STRATEC Molecular (former Invitek) is a major milestone in the history of nucleic acid purification methods.

Ions are ranked in the so-called Hofmeister series according to their ability to denature or stabilize proteins. Protein denaturing ions (chaotropic, “agressive”) such as guanidinium, isothiocyante or chlorate are on one side of the spectrum while protein stabilizing ions (non-chaotropic, “gentle”) such as ammonium, phopshate or sulfate are on the other side of the spectrum.

Using non-chaotropic buffer conditions offers strong key advantages for nucleic acid sample preparation:


1. Time savings through fast protocols

The non-chaotropic binding conditions established by STRATEC Molecular enable binding of nucleic acids using very low salt concentrations down to the low millimolar (mM) range. This is in sharp contrast to binding conditions required by chaotropic chemistry where 100fold or higher concentrations in the molar (M) range are required to achieve efficient nucleic acid binding. Low salt concentrations enabled through non-chaotropic chemistry lead to a reduced number of washing steps in several Invitek products and therefore very fast protocols and time savings.

Efficient binding of nucleic acids using proprietary non-chaotropic buffers used in various STRATEC Molecular kits requires much lower salt concentrations (as little as 50 mM). In several products this results in a reduced number of washing steps leading to faster protocols and/or cleaner DNA.


2. Higher DNA yields from precious samples

The non-chaotropic buffers used in various STRATEC Molecular reagent systems provide improved reaction conditions for enzymes during sample lysis. The gentle chemical environment leads to highly efficient lysis of complex tissues and efficient protein degradation by lytic enzymes. In comparison to guanidium ions (which have a strong protein denaturing effect) the non-chaotropic salts used in various STRATEC Molecular kits actually create a stabilizing environment for lytic enzymes. The long-lasting activity of enzymes in non-chaotropic buffers leads to improved and maximized yields of DNA from complex and difficult samples.

DNA was isolated from 20 mg of rat tissue using the Invisorb Spin Tissue Mini Kit containing non-chaotropic buffers. For comparison with chaotropic chemistry an equivalent kit from a major supplier was evaluated. Standard protocols for both kits were used with comparable conditions for Proteinase K treatment. For both kits the DNA was eluted in 200 µl Elution Buffer and different eluate volumes (1, 2, 3, 5 µl for the Invitek kit; 10 and 20 µl for the other kit) were analyzed on a 0.8 % agarose gel stained with ethidium bromide.

n-c: non-chaotropic conditions (Invisorb Spin Tissue Mini Kit)
c: chaotropic conditions (other supplier)


3. More intact DNA

The non-chaotropic buffer compositions used in various STRATEC Molecular kits provide a chemically more gentle environment for the nucleic acids as compared to buffers based on chaotropic salts such as the frequently used guanidinium salts. As a consequence the DNA purified with STRATEC Molecular non-chaotropic reagent systems suffers less from chemical degradation and often provides more intact DNA. In applications requiring a maximum of intact DNA this is of crucial importance for an optimum assay performance.

Equal amounts of rat tissues were used to isolate DNA using the Invisorb Spin Tissue Mini Kit containing non-chaotropic buffers. For comparison with chaotropic chemistry an equivalent kit from a major supplier was evaluated. Standard protocols for both kits were used with comparable conditions for Proteinase K treatment. For both kits the DNA was eluted in 200 µl Elution Buffer and 5 µl of the eluates were analyzed on a 0.8 % agarose gel stained with ethidium bromide.

n-c: non-chaotropic conditions (Invisorb Spin Tissue Mini Kit)
c: chaotropic conditions (other supplier)


Using non-chaotropic chemistry the DNA bands are broader compared to the DNA from the chaotropic purification protocol. Furthermore, the lower edge of the bands are more diffuse indicating the presence of a continuum of shorter DNA fragments using the chaotropic chemistry.
The key advantages of non-chaotropic chemistry enables the creation of several unique solutions for DNA and viral RNA sample preparation systems for both manual and automated purification. Different optimized non-chaotropic binding conditions are employed in several different STRATEC Molecular kits based on the best fit for the respective sample type.


Furthermore, non-chaotropic chemistry forms the basis for unique sample preparation solutions provided by the product ranges named

MSB - Minimal Salt Binding: fastest protocols without washing steps for DNA fragments,
RTP – Ready to Prep: carrier, lytic enzymes and internal standards all in one tube, stable at room temperature, for pathogen containing samples; and
PSP – Preanalytical Sample Processing: DNA sample stabilization: for stool, swab and saliva samples.