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View additional product information for Pierce™ 16% Formaldehyde (w/v), Methanol-free - FAQs (28908, 28906)
9 product FAQs found
醛类固定剂（例如甲醛、戊二醛）可与各种细胞成分交联，这有助于保持蛋白质和细胞的形态。但一些抗原可能会因交联而被掩藏，需要通过抗原修复的方式暴露掩藏的抗原结合位点。此外，醛类固定剂需要通过通透处理使抗体进入细胞。甲醇和丙酮等有机溶剂可凝聚蛋白质并通透细胞，但细胞形态会受到破坏。表面抗原无需固定即可标记。
We guarantee the functionality of Pierce 16% Formaldehyde (w/v), Methanol-free for one year from date of shipment, if stored correctly. See Limited Warranties for consumables under the General Terms and Conditions of Sale.
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We offer the following crosslinkers for protein to nucleic acids: formaldehyde (Cat. No. 28906), SPB (Cat. No. 23013), SDAD (Cat. No. 26169), sulfo-SDAD (Cat. No. 26175), and sulfo-SBED (Cat. No. A39260).
Formaldehyde can be used for DNA-DNA crosslinking as well as DNA-protein crosslinking. While it is good for crosslinking proteins that are in direct contact with DNA, formaldehyde cannot link proteins that may be bound in a complex with other proteins but are not in direct contact with DNA. EGS or DSG can crosslink proteins to other proteins that are in direct contact with DNA and crosslinked to DNA by formaldehyde.
SPB, Sulfo-SDAD, and Sulfo-SBED are all photoreactive crosslinkers. SPB is an NHS-ester and psoralen heterobifunctional crosslinker that conjugates primary amines on proteins to DNA via photo-activated intercalation of psoralen to pyrimidine bases. The psoralen tricyclic planar ring system intercalates into double-stranded, and to a lesser extent, single-stranded DNA and RNA. The photoreactive psoralen group provides more selective covalent binding to nucleic acids than either phenyl azide or diazerine linkers, which makes SPB the best choice. The diazerine on sulfo-SDAD and the phenyl azide on sulfo-SBED are not selective for nucleic acids and can crosslink other biomolecules in the same besides any protein-DNA interactions. Sulfo-SBED involves biotin transfer rather than actual linking.
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Aldehyde-based fixatives (e.g., formaldehyde, glutaraldehyde) crosslink various cellular components, which helps retain proteins and cell morphology, but some antigens can be masked by the crosslinking, requiring antigen retrieval methods to unmask the antigen binding sites. Also, aldehyde-based fixation requires permeabilization to allow entry of antibodies. Organic solvents such as methanol and acetone condense proteins and permeabilize the cells, but cell morphology can be compromised. Surface antigens can be labeled without fixation.
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The terms “formalin” and “formaldehyde” are often used interchangeably, although the chemical composition of each fixative is different. Formalin is made with formaldehyde but the percentage denotes a different formaldehyde concentration than formaldehyde solutions. For example, 10% neutral-buffered formalin (NBF or simply formalin) is really a 4% formaldehyde solution; the basis for this difference is that historically, formalin was prepared with commercial-grade stock formaldehyde, which is 37 to 40% formaldehyde, by diluting it 1:10 in phosphate buffer.
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Most commercial formaldehyde is prepared with paraformaldehyde (polymeric formaldehyde) dissolved in distilled/deionized water, with methanol added to stabilize the aqueous formaldehyde. Solution stabilization is important to prevent oxidation to formic acid and the eventual repolymerization to paraformaldehyde, and therefore commercial formaldehyde may contain up to 10% methanol. To avoid using methanol-contaminated formaldehyde for fixation, many protocols recommend making “fresh” formaldehyde from paraformaldehyde immediately before sample fixation. This preparation is not necessary if using Cat. Nos. 28906 and 28908.
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We recommend storing in the original container protected from direct sunlight in a dry, cool and well-ventilated area.
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Thermo Scientific 16% Formaldehyde (w/v), Methanol-free is carefully prepared directly from granular paraformaldehyde and sealed under an inert atmosphere in 1 mL and 10 mL ampules. Solution stabilization is important because formaldehyde solutions oxidize to formic acid and eventually repolymerize to paraformaldehyde. Ampule packaging under an inert atmosphere stabilizes the preparation by protecting the solution from both air oxidation and light, allowing access to “fresh” formaldehyde every time. This saves valuable time and eliminates the need and hazards associated with preparing the solution directly from paraformaldehyde. The convenient starting concentration of 16% w/v formaldehyde solution simplifies dilution to the required working concentration.
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Formaldehyde is used as a general IHC fixative and reversible amine-crosslinking agent for cells, protein and nucleic acid tissue samples. As a cell-permeable and reversible protein and nucleic acid crosslinking agent , it couples primary amines that are within proximity of each formaldehyde molecule. Cell permeability allows the reagent to readily enter living cells, enabling intracellular applications such as protein interaction discovery or bioimaging. Formaldehyde crosslinks can be reversed simply by heating the sample.
Find additional tips, troubleshooting help, and resources within our Protein Purification and Isolation Support Center.