Comparison of the cryoprotection of red blood cells by 1,2-propanediol and glycerol

Red blood cells are cooled in buffered solutions containing 10, 15, 20, 30, or 35% ($\text{w}\text{w}$) 1,2-propanediol or glycerol. Cell survival is measured after cooling to ?196 °C at rates between 1 and 3500 °C/min, followed by rewarming rapidly, except in a few cases. At low cooling rates, where the injuries are due to solution effects, for the same ($\text{w}\text{w}$) concentrations of 15 or 20% ($\text{w}\text{w}$), 1,2-propanediol protects erythrocytes better than glycerol. Differences are still observed when the two cryoprotectants are compared on a mole-fraction basis. At high cooling rates the survival passes through a minimum and then increases again. For the same concentrations, the minimum occurs at much lower cooling rates with 1,2-propanediol than with glycerol, in agreement with the better glassforming tendency of 1,2-propanediol solutions. These cooling rates almost coincide with those at which the quantity of ice crystallized begins to decrease in the corresponding solutions. Thus, survival seems to be closely related to the glass-forming tendency at the survival minimum, and at higher cooling rates. After the fastest cooling rates, the warming rates necessary to avoid damage on warming are much smaller than those necessary to avoid devitrification. Therefore, in the present experiments the survivals are not related to the stability of the wholly amorphous state. However, injury follows the presumed transition from cubic to hexagonal ice, in erythrocytes as well as in other kinds of cells.     

Stability of the amorphous state in the system water—1,2-Propanediol

For the same water contents, the stability of the wholly amorphous state of the aqueous solutions of 1,2-propanediol is much greater than that for all the solutions previously studied by us with glycerol, dimethylsulfoxide, ethanol, and ethylene glycol. To the degree that cyroprotection is related to that stability, 1,2-propanediol should be a better cryoprotectant than all these other compounds. The aqueous solutions of 1,2-propanediol have a simple behavior. No hydrate cyrstallizes on cooling, and for intermediate concentrations, on warming, after fast cooling, only ice crystallizes from the wholly amorphous state—first cubic, then hexagonal. The great stability of the amorphous state is shown by the critical warming rates above which no crystallization occurs, as well as by the difficulty in crystallizing on cooling.     

Cryoprotection of red blood cells by a 2,3-butanediol containing mainly the levo and dextro isomers.

A 2,3-butanediol containing 96.7% (w/w) racemic mixture of the levo and dextro isomers and only 3.1% (w/w) of the meso isomer (called 2,3-butanediol 97% dl) has been used for the cryoprotection of red blood cells. The erythrocytes were cooled to -196 degrees C at rates between 2 and 3500 degrees C/min, followed by slow or rapid warming. Up to 20% (w/w) of this polyalcohol, only the classical peak of survival is observed, as with up to 20% (w/w) 1,2-propanediol or 1,3-butanediol. Twenty percent 2,3-butanediol 97% dl can protect red blood cells very efficiently. The maximum survival, of 90%, as with 20% glycerol, is a little lower than with 20% 1,2-propanediol and higher than with 20% 1,3-butanediol. Fifteen percent 2,3-butanediol protects fewer red blood cells than 15% glycerol or 1,2-propanediol, with a maximum survival of about 80%. The best cryoprotection by 30% 2,3-butanediol 97% dl is obtained at the slowest cooling and warming rates, where survival approaches 90%. After a minimum, an increase of survival is observed at the fastest cooling rates, which would correspond to complete vitrification. These rates are lower than with 30%, 1,2-propanediol or 1,3-butanediol, in agreement with the higher glass-forming tendency of 2,3-butanediol 97% dl solutions. In agreement with the remarkable physical properties of its aqueous solutions, the present experiments also suggest that 2,3-butanediol containing mainly the levo and dextro isomers could be a very useful cryoprotectant for organ cryopreservation. However, it would perhaps be better to use it in combination with other cryoprotectants, since it is a little more toxic than glycerol or 1,2-propanediol at high concentrations.     

Inhibition of nucleation and growth of ice by poly(vinyl alcohol) in vitrification solution

Control of ice formation is crucial in cryopreservation of biological substances. Successful vitrification using several additives that inhibit ice nucleation in vitrification solutions has previously been reported. Among these additives, here we focused on a synthetic polymer, poly(vinyl alcohol) (PVA), and investigated the effects of PVA on nucleation and growth of ice in 35% (w/w) aqueous 1,2-propanediol solution by using a differential scanning calorimetry (DSC) system equipped with a cryomicroscope. First, the freezing temperature of the solution was measured using the DSC system, and then the change in ice fraction in the solution during cooling was evaluated based on images obtained using the cryomicroscope, at different concentrations of PVA between 0% and 3% (w/w). Based on the ice fraction, the change in residual solution concentration during cooling was also evaluated and then plotted on the state diagram of aqueous 1,2-propanediol solution. Results indicated that, when the partially glassy and partially frozen state was intentionally allowed, the addition of PVA effectively inhibited not only ice nucleation but also ice growth in the vitrification solution. The effect of PVA on ice growth in the vitrification solution was explained based on kinetic limitations mainly due to mass transport. The interfacial kinetics also might limit ice growth in the vitrification solution only when the ice growth rate decreased below a critical value. This coincides with the fact that PVA exhibits a unique antifreeze activity in the same manner as antifreeze proteins when ice growth rate is lower than a critical value.     

Glass-forming tendency and stability of the amorphous state in the aqueous solutions of linear polyalcohols with four carbons. I. Binary systems water-polyalcohol

All the aqueous solutions of linear saturated polyalcohols with four carbons have been investigated at low temperature. Only ice has been observed in the solutions of 1,3-butanediol and 1,2,3- and 1,2,4-butanetriol. For same solute concentration, the glass-forming tendency on cooling is highest with 2,3-butanediol, where it is comparable to that with 1,2-propanediol, the best solute reported to date. However, the quantity of ice and hydrate crystallized is particularly high on slow cooling or on subsequent rewarming. The highest stability of the amorphous state is observed on rewarming the 1,2-butanediol and 1,3-butanediol solutions. With respect to this property, these compounds come just after 1,2-propanediol and before all the other compounds studied so far. They are followed by dimethylsulfoxide and 1,2,3-butanetriol. The glass-forming tendency of the 1,3-butanediol solutions is also very high; it is third only to that of 1,2-propanediol and 2,3-butanediol. The glass-forming tendency is a little smaller with 1,2-butanediol, but it is cubic instead of ordinary hexagonal ice which crystallizes on cooling rapidly with 35% 1,2-butanediol. Cubic ice is thought to be innocuous. A gigantic glass transition is observed with 45% of this strange solute. 1,4-Butanediol, 45% also favors cubic ice greatly. Therefore, 1,2- and 1,3-butanediol with comparable physical properties are perhaps as interesting as 1,2-propanediol for cryopreservation of cells or organs by complete vitrification. Together with 1,2-propanediol, 1,2- and 1,3-butanetriol, 1,2,3-butanetriol, and perhaps 2,3-butanediol provide an interesting battery of solutions for cryopreservation by vitrification.     

Stability of the amorphous state in the system water--glycerol--dimethylsulfoxide

In aqueous solutions containing both glycerol and DMSO, the various states during rewarming after quenching have been identified by X-ray diffraction. The amorphous state of the whole solution has been observed at very low temperatures. The eutectic was seen by X rays after rewarming only in the solutions containing mainly DMSO. In the other solutions only pure ice has been seen. It crystallizes directly in the hexagonal system, if enough DMSO is present. Otherwise, a mixture of cubic and hexagonal ice appears first. The temperature of the end of fusion and the devitrification temperature were measured with a scanning differential calorimeter for a wide range of warming rates. From these measurements was deduced the stability of the amorphous state, defined by the critical heating rate above which no crystallization occurs. That stability presents no maximum, but increases from glycerol to DMSO for a given water concentration in agreement with the fact that Ashwood-Smith considers DMSO a better cryoprotector than glycerol. But a small amount of glycerol in a solution of DMSO greatly enhances the difficulty of crystallization of the eutectic, without decreasing the stability of the amorphous state of the whole solution by much. Then those containing about 10% ($\text{w}\text{w}$) glycerol/(glycerol + DMSO) are perhaps better cryoprotectants than those with only DMSO, at least for low cooling or warming rates where the eutectic may have enough time to crystallize, eventually with deleterious effects, outside or inside the cells.     

Ternary systems with 1,2-propanediol—A new gain in the stability of the amorphous state in the system water-1,2-propanediol-1-propanol

Three ternary systems with water and 1,2-propanediol were investigated, where the third component is 1-propanol, ethanol, or glycerol. 1-Propanol and ethanol give hydrates in their aqueous solutions as well as in these ternary systems, while glycerol gives none. No gain in the stability of the amorphous state and glass-formation tendency is obtained, for the same water contents, when 1,2-propanediol is partially replaced by ethanol. The gain is negligible when it is partially replaced by glycerol. On the contrary, a large maximum in the stability of the amorphous state is obtained, with a critical warming rate dropping from 10⁸ to 10⁴ °C/min in the presence of 65% (w/w) water when 15% (w/w) of the 1,2-propanediol is replaced by 1-propanol. The decrease in the glass formation tendency due to this replacement and corresponding to a few hydrate crystallization is small. Not only the higher stability of the amorphous state, but also in some cases the replacement of ice crystallization by clathrate crystallization at lower temperatures could perhaps contribute to a better cryoprotection of cells for some cooling and warming rates. The similarities observed between the ternary systems investigated gives an idea of the general behaviour of these systems     

Glycerol and propanediols degradation by Desulfovibrio alcoholovorans in pure culture in the presence of sulfate, or in syntrophic association with Methanospirillum hungatei

Abstract In a mineral medium containing sulfate as terminal electron acceptor, the sulfate-reducing bacterium Desulfovibrio alcoholovorans oxidized stoichiometrically 1 mol glycerol to 1 mol acetate and 1 mol 1,3-propanediol to 1 mol acetate with the concomitant reduction of 0.75 and 1 mol sulfate, respectively; 1 mol 1,2-propanediol was degraded to 0.8 mol acetate and 0.1 mol proprionate, with the reduction of approximately 1 mol sulfate. The maximum specific growth rates (μ_max in h⁻¹) were 0.22, 0.086 and 0.09 with glycerol, 1,3-propanediol and 1,2-propanediol, respectively. The growth yields were 12.7 g, 11.1 g and 7.2 g dry weight/mol 1,3-propanediol, glycerol and 1,2-propanediol degraded, respectively. The growth yields and maximum specific growth rates of the H₂-transferring associations were also calculated. In the absense of sulfate, all these reduced substrates were degraded to acids and methane when D. alcoholovorans was cocultured with Methanospirillum hungatei . Changes in the metabolic pathway were observed in the degradation of 1,2- and 1,3-propanediol. The metabolic efficiency of D. alcoholovorans to degrade glycerol, 1.2- and 1,3-propanediol is discussed.     

Substrate specificity of coenzyme B12-dependent diol dehydrase: glycerol as both a good substrate and a potent inactivator.

The substrate specificity of adenosylcobalamin-dependent diol dehydrase was further studied in detail using an enzyme preparation that appears homogeneous by ultracentrifugal and gel electrophoretical criteria. Besides 1,2-propanediol and 1,2-ethanediol, glycerol, 1,2- and 2,3-butanediol were found to serve as substrate for the enzyme, whereas 1,3-propanediol was not. Of the substrate analogs tested, glycerol displayed some striking features: it was dehydrated to β-hydroxypropionaldehyde with concomitant inactivation of the enzyme. Although the initial velocity with glycerol was comparable to that with 1,2-propanediol, the dehydration reaction ceased almost completely within 3 min accompanying rapid, irreversible inactivation of the holoenzyme. 1,2- and 2,3-Butanediol were converted to butyraldehyde and methyl ethyl ketone, respectively, at a rate much lower than that with 1,2-propanediol. 2,3-Butanediol is the only compound, other than 1,2-diols, known at present to show a considerable substrate activity.     

Cryoprotection of red blood cells by 1,3-butanediol and 2,3-butanediol

1,3-Butanediol and 2,3-butanediol have been used in buffered solutions with 20, 30, or 35% (w/w) alcohol to cool erythrocytes to -196 degrees C at different cooling rates between 1 to 3500 degrees C/min, followed by slow or rapid rewarming. 1,3-butanediol shows the same shapes of red blood cell survival curves as 1,2-propanediol. Having nearly the same physical properties, they have comparable effects on cell survival. The classical maximum of survival for intermediate cooling rates and an increase for the highest cooling rates are observed. This increase seems to be correlated with the glass-forming tendency of the solution. After the fastest cooling rates, a warming rate of 5000 degrees C/min is sufficient to avoid cell damage, but a warming rate of 100-200 degrees C/min is not. Yet both of these rates would be insufficient to avoid the intracellular ice crystallization on warming. The damage on warming after fast cooling seems once again to be correlated with the transition from cubic to hexagonal ice. For all our results, 1,3-butanediol is like a "second" 1,2-propanediol and could be useful as a cryoprotectant for preservation by total vitrification. 2,3-Butanediol always gives extremely low survival rates, though it presents good physical properties. The crystallization of its hydrate seems to be lethal on cooling or on rewarming.     

The use of 1H-NMR spectroscopy and refractometry for investigation of the distribution of nonelectrolytes of N-alcohol series between human red blood cells and extracellular medium

Comparative analysis of 1H NMR spectroscopy and refractometry with respect to their application for investigating the distribution of nonelectrolytes of n-alcohol series (ethanol, 1,2-propanediol, glycerol) and polyethylene glycols (PEGs) with molecular masses of 400, 600, 1500 between human erythrocytes and extracellular medium was performed. The distribution coefficients (Q) for solutions of ethanol, 1,2-propanediol, glycerol, PEG-400, PEG-600 and PEG-1500 were obtained. The Q values decreased with the increase in the nonelectrolyte molecular mass from 1.23+/-0.12 for ethanol to 0.40+/-0.08 for PEG-1500 (1H NMR spectroscopy) and from 2.6+/-0.12 for ethanol to 0.23+/-0.03 for PEG-1500 (refractometry). It was shown that 1H-NMR high-resolution spectroscopy ensures more precise determination of Q values for nonelectrolytes with low molecular masses; for PEGs with high molecular masses, the accuracy of Q value calculation by this method was about 20%. On the contrary, refractometry can be used for investigating substances with high molecular masses; the error of Q value determination for solution of low-refractive substances, such as ethanol, may be more than 50%.     

Proteins in frozen solutions: evidence of ice-induced partial unfolding.

From a drastic decrease in the phosphorescence lifetime of tryptophan residues buried in compact rigid cores of globular proteins, it was possible to demonstrate that freezing of aqueous solutions is invariably accompanied by a marked loosening of the native fold, an alteration that entails considerable loss of secondary and tertiary structure. The phenomenon is largely reversible on ice melting although, in some cases, a small fraction of macromolecules recovers neither the initial phosphorescence properties nor the catalytic activity. The variation in the lifetime parameter was found to be a smooth function of the residual volume of liquid water in equilibrium with ice and to depend on the morphology of ice. The addition of cryoprotectants such as glycerol and sucrose profoundly attenuates or even eliminates the perturbation. These results are interpreted in terms of adsorption of protein molecules onto the surface of ice.     

1,3-丙二醇发酵液后提取技术研究进展

1,3-丙二醇是一种重要的化工原料,以甘油或葡萄糖为原料发酵法制备1,3-丙二醇具有原料可再生、反应条件温和等优点,是近年来国内外的研究热点。由微生物发酵获得的1,3-丙二醇发酵液是含多种强极性的醇及盐类的稀溶液,这使得采用传统的分离方法难以经济、有效地的将1,3-丙二醇从发酵液中纯化出来,后提取过程成为发酵法工业化生产1,3-丙二醇的瓶颈。1,3-丙二醇后提取过程主要包括微生物菌体等高分子物质的去除,盐的去除、回收,有机物的纯化和水的去除。以下对应用于以上分离过程的技术的研究进展进行讨论,提出在该领域应该重视的发展方向。     

Theoretical prediction of devitrification tendency: determination of critical warming rates without using finite expansions

Previously, critical warming rates vcr above which ice did not have enough time to crystallize had been roughly evaluated for many wholly amorphous aqueous solutions. These evaluations were obtained by extrapolation of the linear variation of the devitrification temperature Td with log v, where v is the warming rate, observed experimentally between 2.5 and 80 degrees C/min. Theory also gives such a linear variation, but only using the first term of a finite expansion. The other terms can be neglected only for small variations of Td. These evaluations were sufficient for classification of the solutions, but large errors were made in vcr. A new and more accurate method of determination of the variation of Td with v is presented here. The general equation giving in our models the derivative of the quantity of ice formed versus temperature T is differentiated, instead of integrated using a finite expansion. This gives an explicit expression of v versus Td assuming that the ratio xd of the quantity of ice formed at Td to the total quantity of ice formed on warming is constant. Experimentally, xd is constant within a good approximation. Theoretical curves representing the variation of Td with v have been drawn for solutions of 35 or 45% (w/w) 1,2-propanediol in water. Td never reaches the temperature of the end of melting Tm, but as v tends toward infinity, Td tends toward an asymptotic value of 0.96Tm for 35% solute. For that solution, above about 10(3) degrees C/min, Td deviates appreciably from linearity with log v, but 1/Td remains almost linear with log v up to Td congruent to 0.95Tm. Therefore, systematic comparison of the theoretical variation of Td with v with a linear variation of 1/Td with log v has been done, varying the parameters of the equations within the entire experimental range. Similar conclusions can be given for all the solutions. Experimentally for Td = 0.95Tm, the quantity of ice crystallized is generally less than 0.1% of the solution, reaching 1% only once. Therefore, a new definition of the critical warming rate vcr has been used, corresponding to extrapolation of the linear variation of 1/T with log v up to Td = 0.95Tm. New values of vcr have been calculated for all the binary systems previously studied. The order of the solutions is almost the same, but the new values of vcr are significantly smaller than the former.     

Effects of Organic Solvents and Chemical Modification on the Activity of Glycerol Dehydrogenase

The addition of an organic solvent to the reaction mixture led to a change in the activity of glycerol dehydrogenase. The activity on glycerol decreased to lower than that on 1,2-propanediol. This was due to the apparent increase in the Km value for each substrate. The system was applied to determination of 1,2-propanediol. The standard curve for 1,2-propanediol with a rate assay method was not affected by a 10-fold amount of glycerol in the presence of «-butanol. Chemical modification, except for succinylation of the NH₂-residue, did not cause any change in substrate specificity. The participation of a His-residue in the active site was suggested by the results of chemical modification.     

Fermentation of glycerol to 1,3-propanediol: use of cosubstrates

Three fermentable substances, glucose, 1,2-ethanediol and 1,2-propanediol were checked as cosubstrates for the fermentation of glycerol by Clostridium butyricum and Citrobacter freundii with the aim of achieving a complete conversion of glycerol to 1,3-propanediol. Glucose was fermented by C. butyricum mainly to acetate, CO₂ and reducing equivalents in the presence of glycerol and contributed markedly to the 1,3-propanediol yield. However, because of relatively slow growth on glucose, complete conversion was not achieved. If the two glycols were used as cosubstrates for glycerol fermentation, the 1,3-propanediol yield did not increase but dimished considerably, as they were converted to more reduced products, i.e. alcohols instead of acids. From 1,2-propanediol 2-propanol was formed in addition to 1-propanol. The ratio of the propanols was dependent on the culture conditions.     

Vitrification of bovine blastocysts obtained by in vitro culture of oocytes matured and fertilized in vitro.

Two experiments were conducted to assess the viability of bovine blastocysts obtained by in vitro fertilization of oocytes matured in vitro (IVM-IVF) and cryopreserved by vitrification. In Expt 1, the optimal concentrations of glycerol and 1,2-propanediol in the basic medium (modified TCM199) for cooling and warming without formation of ice crystals were determined by plunging the solution into liquid nitrogen and then warming it in a water bath at 15 degrees C; when both glycerol and 1,2-propanediol were present in the solution (> 45% v/v), vitrification of the medium was observed. In Expt 2, IVM-IVF blastocysts were equilibrated to the mixture of glycerol and 1,2-propanediol (0% to 45%) at 15 degrees C in a stepwise manner as follows: (i) in one step, for 18 min to the final vitrification solution; (ii) in two steps, for 8 min in the first step and 10 min in the second step; (iii) in four steps, for 4 min in the first three steps and 6 min in the last step; (iv) in eight steps, for 2 min in each step, but 4 min in the last step; and (v) in 16 steps, for 1 min in each step, but 3 min in the last step. After removal of cryoprotectants, the blastocysts were cultured for 24 h in vitro. The survival rates for the embryos equilibrated in 1, 2, 4, 8 and 16 step(s) were 56, 89, 100, 100 and 100%, respectively. The blastocysts equilibrated in 1, 2, 4, 8 and 16 steps were vitrified by plunging the straws containing them into liquid N2, thawed and cultured in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glass-forming tendency in the system water-dimethyl sulfoxide

The glass-forming tendency on cooling and the stability of the wholly amorphous state on warming have been previously reported for many cryoprotective solutions. However, unlike the other solutions, those of dimethyl sulfoxide (Me(2)SO) have not been studied on cooling. In this paper, the glass-forming tendency of Me(2)SO aqueous solutions has been measured for solutions containing 40, 43, 45, and 47.5% (w/w) Me(2)SO. At a concentration of 45% (w/w), the glass-forming tendency decreases in the following order: levo-2, 3-butanediol, 1,3-butanediol, 1,2-propanediol, 1,2,3-butanetriol, dimethyl sulfoxide, dimethylformamide, diethylformamide, 1, 4-butanediol, ethylene glycol, glycerol, 1,3-propanediol. New measurements have also been made on warming the Me(2)SO solutions.     

1,3-Propanediol:NAD+ oxidoreductases of Lactobacillus brevis and Lactobacillus buchneri.

In the cofermentation of glycerol with a sugar by Lactobacillus brevis and Lactobacillus buchneri, a 1,3-propanediol:NAD+ oxidoreductase provides an additional method of NADH disposal. The enzyme has been purified from both L. brevis B22 and L. buchneri B190 and found to have properties very similar to those reported for the enzyme from Klebsiella pneumoniae. The enzymes required Mn2+ and are probably octamers with a molecular mass of 350 kDa. Although not absolutely specific for 1,3-propanediol when tested as dehydrogenases, the enzymes have less than 10% activity with glycerol, ethanol, and 1,2-propanediol. These properties contrast sharply with those of a protein isolated from another Lactobacillus species (L. reuteri) that ferments glycerol with glucose and previously designated a 1,3-propanediol dehydrogenase.