Light amine protection

Hindered Amines. Hiadered amines are extremely effective ia protecting polyolefins and other polymeric materials against photodegradation. They usually are classified as light stabilizers rather than antioxidants. 

Oligomeric hindered amine light stabilizers are effective thermal antioxidants for polypropylene. Thus 0.1% of A[,Af-bis(2,2,6,6-tetramethyl-4-piperadinyl)-l,6-hexanediamine polymer, with 2,4,6-trichloro-l,3,5-triazine and 2,4,4-trimethyl-2-pentaneainine [70624-18-9] (35) (Fig. 5), protects polypropylene multifilaments against oxidation when exposed at 120°C in a forced-air oven (22) for 47 days. 3,5-Di-/ l -butyl-4-hydroxytoluene [128-37-0] (0.1%) affords protection for only 14 days. 

An alternative mechanism by which additives may protect polymers from photo-oxidation is radical trapping. Additives which operate by this mechanism are strictly light stabilizers rather than antioxidants. The most common materials in this class are the hindered amines, which are the usual additives for the protection of poly (ethylene) and poly (propylene). The action of these stabilisers is outlined in Reactions 8.3-8.5. 

More than 200 users annually consume over US 55 million of light stabilisers. IR absorbers (e.g. amine, antimony salt mixture) protect against IR radiation applicable in PC, PMMA, PVC, etc. 

One of the more important protective mechanisms is probably the ability of these substances to interact not only with various oxygen-centered radicals but also with hydroperoxides. This ability is supplemented by the formation of associates between the amine light stabilizer and species responsible for polymer degradation. 

In use, SAND is first reacted with an amine-containing protein or other molecule—being careful to protect the photoreactive group from inadvertent degradation by exposure to excessive room light or sun. The modified intermediate then is allowed to interact with a target molecule. Finally, the photolyzing process is done to effect a nonselective crosslink between the... 

Since the active ester end of the molecule is subject to hydrolysis (half-life of about 20 minutes in phosphate buffer at room temperature conditions), it should be coupled to an amine-containing protein or other molecule before the photolysis reaction is done. During the initial coupling procedure, the solutions should be protected from light to avoid decomposition of the phenyl azide group. The degree of derivatization should be limited to no more than a 5- to 20-fold molar excess of sulfo-SBED over the quantity of protein present to prevent possible precipitation of the modified molecules. For a particular protein, studies may have to be done to determine the optimal level of modification. 

Modify a purified bait protein by adding an aliquot of crosslinker to achieve a molar excess of 2-10 moles per mole of protein (protect from light). For NHS ester-containing reagents, react in 0.1 M sodium phosphate buffer at pH 7.2-7A. Avoid using any other amine-containing buffer components, such as Tris or imidazole, which will interfere with the reaction. 

In carbohydrate chemistry, the most described method for the preparation of saccharidic thionocarbamates involves preliminary introduction of the amine function on a partially or non-protected saccharidic template. The condensation of amino sugars with carbon disulfide or thiophosgene leads to cyclization in 1,3-oxazolidine- or l,3-oxazine-2-thiones. This reaction involves the formation of an intermediate isothiocyanate, which reacts further with a 3- or y-located hydroxyl group. The viability and facility of this process depends on the saccharidic ring size and the inherent strain. Some major rules can be put into light from the cases studied 30... 

Grelier etal. (1997) synthesized a variety of UV stabilizers based upon hydroxy-phenylbenzotriazoles incorporating an isocyanate functionality. These were reacted with wood using microwave energy. The modified woods were exposed to UV irradiation and the photoinduced discolouration determined. It was found that the best protection was obtained when the UV stabilizer was used in conjunction with polyethylene glycol, or hindered amine light stabilizers. 

A -(2-Chloro-l,l,2-trifluoroethyl)-/V,/V-diethylamine (2) is a very hydroscopic liquid which can be stored for several days without significant loss of fluorinating activity, only when protected from moisture and light. It is synthesized through the addition of diethylamine to the C = C bond of chlorotrifluoroethene (l).13-16 Other amines have also been added to chlorotri-fluoroethene (1) to give analogous reagents 17 however, these have found little application. 

Reaction of AMCA-NHS with proteins proceeds efficiendy in the pH range 7—9. Avoid buffers containing amines that can compete in the coupling reaction, such as Tris or glycine, and avoid imidazole buffers since they promote hydrolysis of the NHS ester. AMCA-NHS is relatively insoluble in aqueous buffers. The compound must be first dissolved in organic solvent prior to addition of a small aliquot to the reaction mixture. A concentrated stock solution may be prepared in DMSO and stored up to 2 weeks refrigerated or frozen without loss of activity. The solid and all solutions of AMCA-NHS should be protected from light to avoid photodecomposition of the fluorophore. 

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