104
FREEZE-DRYÏNG
growth, virus was harvested and puried by : l) Adsorption to and elution from chicken
red blood cells, 2)—high—speed differential centrifugation, or 3) adsorption and elution
from ion exchange resins.
In studies of the effects of freezing or freeze-drying on materials of biologie origin, two
_
elements of the total system must be considered : l) Internal factors dependent on the
_
nature of the bielOgic system and 2) external factors which determine the rates at which
energy is removed from the biologie system during freezing and the rates at which energy
is returned to the system during drying. As regards to the rst, the generative centers
_
for ice formation and the distribution and growth of crystalline nuclei will be inuenced
by water content, concentration of solutes and dispersed phase of the system, and by the
structure and shape of the specimen. External factors which can inuence the rates of
cooling or drying include the absolute temperature and the specic heat of the cold source,
and the thermal contact between the body being cooled and the refrigerating system.
Suspensions of viruses, by their very nature, permit a degree of freedom for modifying
the factors above that is found in few other biologie materials. Because we are dealing
_
primarin With entities of submicroscopic dimensions With similar and equal surface charges,
viruses tend to be dispersed homogeneously throughout the suspending medium. Since the
Ïf;â
liquid phase of the suspension is many times greater than the solid phase, containers of
many shapes can be used. It is even possible to obtain virus particulates embedded in
vitreous ice by spraying suspensions on metal plates maintained at low temperatures.
Finally, because We are using as starting material, suspensions of viruses of high relative
activities, it is possible to work comfortably and aCcurately With small samples of the
;Î
order of 0.1 ml. Thus the effects of varying conditions of freezing and freeze-drying on the
activities of the suspensions of viruses can be determined With a precision diicult or
impossible to attain in the majority of biologie systems.
'
_
CHARACTERISTÏCS OF VIRUSES
‘
COnsidering the diversity of viruses
biological, morphological and chemical
variations, it might appearimprobable on cursory examination to categorize their divergent
Organization in terms of fundamental characteristics. Fortunately, sufcient information
ConCerning the checalcomposion and the morphologie structure of virus particles is
_
now available to permit a reasonably satisfactOry:grouping of the majority of animal
viruses; Inour studies seeking a relationship between the physico—chemical characteristics
of_ Viruses and the
storage.
low temperatures, and freeze—drying on
theirstability, We have…useduthe following
the basis for
Ï
.
_
-
_
5
,
,
_
.
_
…
M'
*
NuclezcAcszype, as dened by 'LWo' et al., the
are. constructed
'
:àÇid °°ËÔ..°IlÇlÛSÔd—în a protein coett,the core consisting of
'
'
d(RNA)dybl
(PNALJbùt“nôtübath;
_
115
…
.
* à
-;
treatment
as ether, chloroform or
'
d11uœ sOlutio8 }…of }:dete‘rgents;_:;destroysil lthQ»ifcäetivitÿ-i ofsomev1ralagents =td has» 310
FREEZE-DRYÏNG
growth, virus was harvested and puried by : l) Adsorption to and elution from chicken
red blood cells, 2)—high—speed differential centrifugation, or 3) adsorption and elution
from ion exchange resins.
In studies of the effects of freezing or freeze-drying on materials of biologie origin, two
_
elements of the total system must be considered : l) Internal factors dependent on the
_
nature of the bielOgic system and 2) external factors which determine the rates at which
energy is removed from the biologie system during freezing and the rates at which energy
is returned to the system during drying. As regards to the rst, the generative centers
_
for ice formation and the distribution and growth of crystalline nuclei will be inuenced
by water content, concentration of solutes and dispersed phase of the system, and by the
structure and shape of the specimen. External factors which can inuence the rates of
cooling or drying include the absolute temperature and the specic heat of the cold source,
and the thermal contact between the body being cooled and the refrigerating system.
Suspensions of viruses, by their very nature, permit a degree of freedom for modifying
the factors above that is found in few other biologie materials. Because we are dealing
_
primarin With entities of submicroscopic dimensions With similar and equal surface charges,
viruses tend to be dispersed homogeneously throughout the suspending medium. Since the
Ïf;â
liquid phase of the suspension is many times greater than the solid phase, containers of
many shapes can be used. It is even possible to obtain virus particulates embedded in
vitreous ice by spraying suspensions on metal plates maintained at low temperatures.
Finally, because We are using as starting material, suspensions of viruses of high relative
activities, it is possible to work comfortably and aCcurately With small samples of the
;Î
order of 0.1 ml. Thus the effects of varying conditions of freezing and freeze-drying on the
activities of the suspensions of viruses can be determined With a precision diicult or
impossible to attain in the majority of biologie systems.
'
_
CHARACTERISTÏCS OF VIRUSES
‘
COnsidering the diversity of viruses
biological, morphological and chemical
variations, it might appearimprobable on cursory examination to categorize their divergent
Organization in terms of fundamental characteristics. Fortunately, sufcient information
ConCerning the checalcomposion and the morphologie structure of virus particles is
_
now available to permit a reasonably satisfactOry:grouping of the majority of animal
viruses; Inour studies seeking a relationship between the physico—chemical characteristics
of_ Viruses and the
storage.
low temperatures, and freeze—drying on
theirstability, We have…useduthe following
the basis for
Ï
.
_
-
_
5
,
,
_
.
_
…
M'
*
NuclezcAcszype, as dened by 'LWo' et al., the
are. constructed
'
:àÇid °°ËÔ..°IlÇlÛSÔd—în a protein coett,the core consisting of
'
'
d(RNA)dybl
(PNALJbùt“nôtübath;
_
115
…
.
* à
-;
treatment
as ether, chloroform or
'
d11uœ sOlutio8 }…of }:dete‘rgents;_:;destroysil lthQ»ifcäetivitÿ-i ofsomev1ralagents =td has» 310