the present invention should be suitable for use with all type ii restriction endonucleases . our tests have been conducted on a variety of different restriction endonucleases ( hae iii , pal i , pst i , eco ri and hinf i ). these particular enzymes were selected as examples for study because they are commonly used enzymes that are known to exhibit star activity . by the term &# 34 ; glassified &# 34 ;, we mean an under - cooled liquid with a very high viscosity . a glass normally presents an extremely slow diffusive process . the glass transition temperature , &# 34 ; t g ,&# 34 ; defines the temperature at which a glass changes phase . upon temperatures higher than the t g , a rubber - like material is formed from the glass . if the temperature continues to increase , the material eventually becomes a fluid . compounds with a higher t g will remain at a glass stage at higher temperatures . residual moisture in the glass will depress a t g value . the preferred glassified composition is composed of a suitable stabilizer that is hydrophilic , so that water can readily dissolve the glass and present the restriction enzyme in an aqueous solution . the stabilizer substance should typically display a t g in a range from 20 ° to 180 ° c ., preferably 30 ° c . to 80 ° c . if the t g of a glass is well above average room temperature , the glass is better able to withstand storage on a laboratory shelf where the actual temperature may vary somewhat . the t g of a formulated composition is typically 5 ° below the t g of the stabilizer . preferably , the stabilizer substance will be chemically inert towards the restriction enzyme . carbohydrates ( e . g . polyhydroxy aldehydes or ketones , such as those with a ( ch 2 o ) n empirical formula , and their derivatives ) are suitable stabilizers . preferred carbohydrates may be either sugars or polysaccharides . suitable carbohydrates may be either linear or branched , and may have one or more sugar moieties linked via various linkages . particularly preferred carbohydrate stabilizers are polysaccharides such as ficoll , dextran and trehalose . ficoll is a highly branched polymer that has a molecular weight of 5000 to 1 , 000 , 000 and is made by copolymerization of sucrose and epichlorohydrin . a particularly advantageous form of ficoll is ficoll 400 which has a molecular weight of 400 , 000 . ficoll is commercially sold by pharmacia . fig1 depicts ficoll . see also u . s . pat . no . 3 , 300 , 474 . other suitable sugars and polysaccharides with appropriate tg values are maltose , sucrose , cellobiose , maltotriose , polydextrose , mannitol , sorbitol and inulin . c . formation of glassified restriction enzymes the general process of glassification involves first combining an aqueous solution of the restriction enzyme with a supply of the stabilizer . preferably , the restriction enzyme preparation is free of glycerol ( or prepared at a concentration of less than 1 % glycerol ). the stabilizer is present at a concentration of at least 10 % by weight , preferably 30 %. when higher concentrations of enzyme are used , it is preferable to use more ficoll . for example , when more than 100 units pst i are present per 50 μl of rehydrated reaction mixture , the stabilizer substance is preferably at least 30 % ( w / w ) ficoll . the level of enzyme giving rise to star activity varies from enzyme to enzyme . in this regard , a high concentration of certain stabilizers such as ficoll can surprisingly permit high concentrations of enzymes to be used for cleavage without significant star activity . note that wholly apart from the effect of glycerol , many restriction enzymes in the prior art exhibited star activity when present in high concentration in a dna cleavage reaction . the restriction enzyme is preferably glassified in the presence of a complete reaction buffer , as opposed to a standard storage buffer . unlike conventional storage buffers which omit mgcl 2 , a restriction enzyme reaction buffer contains all components necessary to facilitate a restriction enzyme digestion . such components usually include optimized amount of various salts , such as tris - hcl , kcl ( or nacl ), dtt , edta ( and sometimes triton x - 100 , bsa , and / or beta - mercaptoethanol ). in particular mg + 2 , preferably as mgcl 2 , should be included in the reaction buffer because restriction enzymes require this ion . it should be noted that mg + 2 had not previously been incorporated into standard storage buffers because of the perceived problems associated with increased protease activity and contaminating bacterial growth in the presence of mgcl 2 . the restriction enzyme / buffer formulation is processed into a glass or amorphous state by evaporation of water in a vacuum , preferably at room temperature , followed by additional removal of water at 50 ° c . the final formulation preferably contains less than 4 % water and has a glass transition point of at least 30 ° c . the resulting formulation should be stable at room temperature for extended periods . for convenience , the restriction enzyme / buffer formulation may be placed into individual tubes in amounts sufficient for a single enzyme digest . to carry out a restriction digestion using the glassified restriction enzyme , the dna substrate and water is introduced into a tube containing the glassified composition . the water quickly dissolves the glassified enzyme . restriction digestions can then be carried out at standard temperature and time of incubation , such as those described in t . maniatis pages 5 . 3 - 5 . 32 , &# 34 ; restriction and dna methylation enzymes &# 34 ; in molecular cloning ( 1989 ). ( this article and all other references are hereby incorporated by reference as if the reference were set out herein .) hae iii restriction enzyme may be obtained commercially . one should first dalyze the commercial preparation to remove glycerol . preferably , ficoll or another stabilizer is added before dialysis . as an alternative , we isolated hae iii through standard column chromatography methods . it will be appreciated that other type ii restriction enzymes are available and could instead be used . the enzyme was initially stored in the following glycerol - less buffer : ______________________________________ 10 mm tris - hcl ( ph 7 . 5 ) 50 mm kcl 1 mm dtt 0 . 1 mm edta 20 % ficoll______________________________________ the enzyme was then titrated to determine unit concentration . a &# 34 ; unit &# 34 ; of hae iii is defined for purposes of this patent as the amount of enzyme needed to hydrolyze 1 μg of lambda dna to completion in 60 minutes at 37 ° c ., in a total assay mixture of 50 μl . one particular batch of enzyme we examined was 50 u / μl . the preferred enzyme concentration is greater , but almost any concentration is suitable for use in the present invention . in the case of our 50 u / μl hae iii sample , after determining the enzymatic units , the following additions were made to individual 1 . 5 ml eppendorf polypropylene tubes : ______________________________________ hae iii bsa storage reactionhae iii / tube ( 50 u / μl ) ( 10 mg / ml ) buffer buffer______________________________________100 units 2 μl 0 . 5 μl 18 μl 10 μl500 units 10 μl 0 . 5 μl 10 μl 10 μl reaction buffer is : 250 mm tris - hcl ( ph 7 . 6 ) 250 mm kcl 50 mm mgcl . sub . 2______________________________________ the samples were then dried in a vacuum oven at a vacuum of 25 in . hg , room temperature , overnight ( primary drying ). the next day , drying was continued at 50 ° c ., 25 in . hg for 2 hours ( secondary drying ). the tubes were capped under nitrogen and stored at room temperature in a desiccator . after storage , we dissolved the glassified composition in 50 μl of filtered , sterile water containing 1 μg of the dna template . in a particular experiment , the dna template was φx174 dna . any dna preparation is suitable for the present invention . by &# 34 ; dna &# 34 ; we mean naturally occurring dna and synthetic dna , as well as derivatives thereof , such as methylated or radiolabelled versions . the reaction tube wa incubated at 37 ° c . for approximately 12 hours . this digestion time could be shortened by the addition of more enzyme . after digestion was completed , the reaction was halted by adding 10 μl of a known stop reagent ( 0 . 05 % bromphenol blue , 0 . 1 m edta , and 50 % glycerol ). samples of reaction mixtures were electrophoresed in known fashion into an agarose gel ( e . g . a 1 . 1 % agarose in tbe buffer ). the electrophoresis was run for two hours at 180 v . the gel contained 0 . 1 μg / ml ethidium bromide to make the dna fragments visible under uv light . examination of the electrophoretic gel disclosed complete digestion of sample dna by all reconstituted hae iii samples . no star activity was observed in any sample . we have also examined the restriction enzymes pal i , eco ri , pst i and hinf i . the enzymes were removed from storage buffer , and a reaction buffer containing ficoll was substituted . when tested , all enzymes exhibited complete enzymatic activity and a lack of star activity in the presence of ficoll . thus , it appears that ficoll affirmatively reduces star activity . for dna type analysis ( e . g . paternity testing ), one compares restriction digests of two different dna samples . because of reduced star activity , introducing the results of these digests as evidence in legal proceedings should be facilitated because the digests are more definitive . it should be appreciated that the invention will work with a wide variety of dna samples by using the compositions of the present invention in place of the refrigerated prior art compounds . in optimizing the reaction buffers for other restriction enzymes , one may begin by examining the reaction conditions already used , but omitting glycerol . thus , the invention is intended to be useful for a wide range of dna and enzymes .