Abstract: Reported is the shape of two dimensional gels of protein separation produced by electropheses in the years 1982 to 1983 and stored in a cool room at approximately 4° C until the year 2017 ( i.e. produced more than 30 years ago). The gel were stored in cases of metall which had a seal protection to avoid exchange humidity with the environement. The mayority of gels were coumassie stained with a few siver stained ones. Many of the gels were still well maintained so that they could be analysed. For the well maintained exemplars the condition of storage are spezified.

History: 1982 and 1983 are early times were proteins were separated by two dimensional gel electrophoreses. The probes separated by the gel electrophoreses were of different origin depending on the goal of the investigation. Originally the gels were saved in a cool room for later inspection until the research series was completed. Later the gels had to be transfered because of construction events to a new cool room. At this time the gels were packed into two cases of metal shielded against humidity.

storage of the gels

fig. 1 the two metall cases in which the gels were stored for years subfigure a and b and a view at their content subfigure l c and d.

In the new cool room they stayed until the year 2017 when there was a mayor cleanup. Before the gels were disposed they were analysed and the result is reported here.

Material: The gels were produced by two dimension electrophoreses (see Das et.al.) and stained by the methods of coomassie or of silver.

single gels of small size 4x4 cm

fig. 2 gel of dimension 4 by 4 cm (small sized) on which protiens are visualized as blue spots by the stain coomassie (two left subfigures of the figure) and silver stain (one on right)

single gels of size ~8x8 cm

fig. 3 gel of dimension 8 by 8 cm (bigger size) proteins spots are visulized with coomassie blue stain (left). Gels stained with silver stain did not show spot pattern anymore (right)

The size of the gels was quadratic and was mainly either ~4 x 4 cm or ~8.5 x 8.5 cm. For details of the apparatus and the procedure to produce the gels (see Das et. al.). The proteins separated were of different origine and their analysis is not subject of this discussion which is supposed to deal with conservation of the gels state. The gels are enclosed with the fixation gemisch for storage in a platic bag of material of different origine and thickness (usually used in freeze of goods or in covers to mail) and sealed by a heat device. The bag carries information on it. Usually it is labelled (see fig.3)

e.g. by the date of electrophoreses and sometimes in addition the time the probe of protein was prepared (taken) and by specifying the micro organismen of the probe. Also, the direction of the electrophereses voltage is marked as + and -. By these labels the experiment from which the probe originate may be traced back in the labor journal or a publication.

Method of storage: Figure 1 shows interior of the metall case. There is one cardboard box in the metal case and around it several platic bags in which some of the platic covered gels are placed. In the cardboard box the plastic covered gel are stapeled on top of each other. To fill the box some gels are place head up at the left space.

Method of visualisation: It was not intended to quantify the protein spots on the gel but rather to evaluate the conservation of the gel itself and its value for analysing it in the present state. The method of scanning the gels (by A3-scanner Brother 6510 DW) was given preference over the photographic one since the equipment was at hand and could be processed furtheron with the software (GIMP) as files of type ".tif". One scan at 600 dpi comprises 6 bags with a gel (see fig. 4).

a well conserved set of gels

fig. 4 scan at 600 dpi by 600 dpi of 6 bags with a gel displaying the state of the gels and the protein spots in it.

Several gels let steam up the glas plate of the scanner beneath them because they cooled it. This could be seen on the scans hardly only.

Result: On silver stained gels either of the small size nor at the bigger size no longer spots of protein could be identified even if the gel itself is well conservered (see fig. 3). Whereas the coomassie stained protein spots are well visible and seemed to be fixed at their position. Probably, these gel could be analysed again either for the position or the quantity of protein in the spot (see fig. 4). However, there are a lot of gels which are deformed, split, have lost fixation liquid, are dryed and some even are swollen by evaporating the liquid (see fig. 5 for examples).

a not well conserved set of gels

fig. 5 scans at 600 dpi by 600 dpi of 6 bags displaying examples of different kinds of damaged gels during the period of storage.

These gels are often very fragile, too. The origin of the distortion of these gels has not be evaluted further but may rise from different causes. Apparently a mayor fault was the thickness of the material of covering bag of the gel. Nearly all gels put into a thin walled platic bag were not conservered well. At the time of none of the scanned gels a picture is available of the early days showing the spot pattern. A comparision of the spot pattern at early days and aproximately 30 year later would complet the invetigation. It seems that a surplus in fixation liquid dessolves coomassie blue stain and diffuses it upon the liquid. To show the gels without being covered by bags scans are taken at 2400 dpi resolution (see figure 6 and figure 7)

gels scanned at 2400 dpi

fig. 6 On left panel a bag covered gel taken from the scan file://I:\Gele\Figures\Gel59.tif is displayed. Removing its bag shows the same gel at the right panel.

gels scanned at 2400 dpi

fig. 7 On left panel a 2400 dpi scan of a gel from the scan of Gel112 of multiple files from which the bag has been removed. On the left side the same gel is scanned in grey scale mode.

The spots are well consered and could be located as well as determined in intensity. At higher magnification one visualises that at least smaller spot had got a little bit diffuser. But this could be judged with a comparison picture when the gel was produced. The scan taken in gray scale mode display spots well bounded but the very intense spots touch the saturation region of the grey scale.

Conclusion: The conditions for gels which are conservered well are: 1. their bags were packed on top of each other in the cardboard box forming a stack with no intervall between the bags of gels and no surplus of fixation liquid inside the covering bag. The very well conservered gels were placed in thick walled platic cover used as DIN A4 laminate material or used for covers of sheets of paper(see figure 8).

fig. 8 an example of packed gels in a rigid cover with a little amount of fixing liquid. Thin walled bags lost liquid and tend to distoriate the gel structure.

Standard of comparison: The gel of figure 9 is included to allow a comparison with the protein pattern of serum of blood which should be easily available.

fig. 9 a gel of the year 1982 displaying the protein pattern of blood serum (see fig. 3 middle picture also).

Appendix: The compete data base of scans (approximately 11.5 GB as file GelDB.zip) is accessible here download .

The original (600 dpi and 2400 dpi scans) are distributed among the cases (see figure 1): Gel01 to Gel24 are scans from gels packed around the cardboard box (see figure 1), Gel25 to Gel64 were in the cardboard box (see figure 1 left) and Gel65 and up in the cardboard box (see figure 1 right).