AKI Cryovials Protect Crystal Protein Growth

A K Industries (AKI) produces a polypropylene, cryogenic viral subassembly for Molecular Dimensions, whose business offers intelligent solutions for protein crystal growth. The tubular container, 38mm long with a 13mm outside diameter, is used during the analytical process of protein crystallisation X-ray diffraction. Essentially, the vial protects a protein crystal growth while it is being robotically transferred. The vial has been developed to increase throughput where samples can be automatically placed for testing, analysed and lifted back into a rack unit.

The pole-orientated (anisotropic), neodymium iron boron permanent ring magnet, which is insert-moulded into this cryogenic vial (cryovial) by AKI, holds in place the cryocap, from which the sample is suspended as the vial is moved by transfer robot. Then a circular, galvanised steel weight, insert-moulded by AKI into its base, orientates the vial and assists with its location in the rack. At present the ballast disc in question is non-magnetic, although Molecular Dimensions' product specification indicates that it may be magnetised.

AKI's production tool incorporates two sintered, aluminium nickel cobalt (Alnico) permanent magnets for retaining both inserts as well as checking the polarity of the ring insert. They feature high corrosion resistance well-suited to the harsh operating conditions of a continuous process. The first Alnico magnet is located on the fixed half of the tool and lies at the base of the core that creates the vial form. This magnet is polarised in such a way that it will attract the ring magnet, which is inserted and moulded into the product.

If the magnet to be insert-moulded is placed onto the core with incorrect polarity, then it will be repelled by the magnet in the tool. The second magnet is located inside the tool cavity on the moving half of the tool; the purpose of this magnet is to retain the ballast weight during the moulding process. The magnetic cryovial moulded by AKI also incorporates a round vent hole each side below the ring magnet through which liquid nitrogen can 'boil off'. Magnetic cryovials have a magnetic ring that holds the Cryocap in place.

Rounded edges (or chamfers) on top and bottom of the vials avoid potential blocking during robotic transfers. A ferromagnetic disc at the bottom of the vial provides 'positive' vial manipulation with a magnet. There is a vent hole through which liquid nitrogen can 'boil off'. The cryocap and magnetic cryovial system is compatible with commercial sample changers using magnetic-style sample holders. Cryocaps are available both with and without identification with ECC200 Data Matrix codes plus human-readable code.

The system has been manufactured to published SPINE standards for improved precision for robotic handling, and improved stability for use with micro crystals. However, the system can also be used manually.

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