Micelle Formation – From Arc to Sphere.

By

Peter Gauthier

Peter Gauthier, Ph.D. Email: peterspond@roadrunner.comDept. Science (retired)Mount Saint Mary’s CollegeEmmitsburg, MD 21727

Micelle Formation – From Arc to Sphere.

Abstract

In this article, arguments are made for the growth of a micelle from a small arc to a complete sphere. This mechanism provides for the inclusion of an aqueous phase, which may be entrapped within the finished structure. If such an aqueous phase can exist in the finished sphere, then a simple micelle could have been the first biotic structure.

It is also possible that a micelle can form in this fashion without entrapping any water. The mechanism of formation is the same, growth of small arcs to complete spheres by the addition of fatty acid sub units, but without an aqueous phase. Such a model could not accommodate the early molecules of life and the micelle therefore could not be considered the first biotic entity, since it would lack water, and therefore could not include the water soluble molecules needed for the perpetuation of this entity.

To postulate the micelle as the first biotic entity, the existence of an aqueous phase is essential for the interaction of water soluble molecules. Otherwise, one may assume that the first biotic structure consisted of a double layered membrane with properties similar to those in existing cells, and contained a substantial aqueous core within which living molecules could interact and evolve.

Micelle Formation – From Arc to Sphere

If the first biotic structures consisted of double layered membranes such as in modern cells, then there naturally existed an aqueous center that would accommodate the evolving molecules of life. But if the original biotic entity consisted of a single layered membrane such as exists in the micelle, then the presence of an aqueous phase is not evident in most depictions of the micelle.

When pictured as a finished entity, the micelle does not contain an aqueous center, since the fatty acid chains extend to its center and dissolve in one another including those of the opposing side of the sphere with which these chains share the center of the micelle.

The arrangement of polar and non-polar groups are often pictured in the manner illustrated below in Figure 1.

Figure 1.The Micelle

= Polar Head = Hydrophobic Chain

The outer membrane of the micelle is made up of the charged, hydrophilic carboxylate groups of the fatty acids, and the long hydrophobic chains extend to the center of the sphere. In this model there is no provision for an aqueous phase, since all the space is occupied by the fatty acid chains.

It is obvious that the long hydrophobic chains tend to dissolve in the center of an existing micelle, when we visualize the final form, with attending hydrophobic interactions, and the cementing action of van der Waal’s attractive forces as illustrated in Figure 1.

But the question to be answered is, can a Micelle accommodate an aqueous phase? Hypothetically, it would seem that it can, and Figure 2 illustrates a mechanism whereby an aqueous phase can be located in the center of the finished Micelle.

Figure 2. Developing Micelle

Legend: Sub Unit Hydrophilic Group Hydrophobic Group

Figure 2A Figure 2B

Figure 2C Figure 2D

Figure 2E Complete Micelle

Discussion of the developing micelle illustrated in Figure 2.

The Micelle originates with a few amphipathic substances coming together to form the first arc of the sphere to be, as illustrated in Figure 2A. In this stage of development, the long chains of fatty acids would tend to dissolve into the proximate neighbor chain, since these chains have no affinity for the hypothetical center at all, since at this stage this is purely an aqueous medium.

As more of the sub units coalesce, and the existing arc is extended, the newly added hydrophobic chains would tend to dissolve in the fatty acids already present, and avoid the aqueous phase. There is a limited encroachment on the center to be, but the natural tendency of these hydrophobic chains would be to avoid the aqueous future core at this time in the development of the Micelle.

With the Micelle half finished, Figure 2B, there could still exist an aqueous pocket in the center to be, since the incoming fatty acid chains would more easily dissolve into the existing adjacent chains, held there by van der Waal’s forces, than in the aqueous core of the future sphere.

As the Micelle continues to develop, the sub units continue to arrange themselves in the prescribed order, with the hydrophilic groups making up the outer border of the membrane, and the long chains extending into the interior of the developing sphere, but still avoiding the aqueous center.

In the stage of development illustrated in Figure 2C, it is evident that the hydrophobic chains now tend to extend further into the aqueous core and displace the water in that region. The chains have a greater tendency to extend into the core now, and the medium in the vicinity of the center is getting more crowded as the fatty acids are expanding their domain, and excluding more and more of the aqueous phase in this segment of the micelle.

As the final arc of the spherical micelle is completed, as illustrated in Figure 2D, and the charged groups nestle into the outer membrane, the fatty acids can now dissolve into the existing chains, and also with other incoming fatty acids. At this point of micelle development, an aqueous phase could be trapped within the micelle, and could include hydrophilic molecules already present in this aqueous phase. Hypothetically, simple molecules of energy generation such as glyceraldehyde, could be present in this aqueous phase.

Once the micelle membrane is complete, the aqueous phase trapped within its borders would probably find its most stable position equidistant from all hydrophobic groups, namely in the core center of the micelle.

Why is the center of the micelle the most stable place for the aqueous center? The last sub units to coalesce and finish this particular sphere have trapped within the structure an aqueous phase that is initially off center. But the last hydrophobic chains that finished the sphere have as great a tendency to extend themselves as their counterparts on the other side of the finished micelle so the sphere is not a stable entity at this point.

It seems logical to assume that all the hydrophobic chains would exert the same repulsive force against the aqueous region. Therefore, as those last chains extend themselves to the same degree as their counterparts on the opposite side, the sphere would tend to bulge out on the last section to form. So the aqueous phase itself is really stationary, it is the sphere that is still growing in volume as it bulges out on the last side to be formed, until all the forces exerted against the aqueous phase are equal. This occurs when all hydrophobic chains are equally extended, at which point the aqueous phase is centrally located providing that all chains are of the same length.

A centrally located aqueous core therefore, would seem to represent the most stable situation and a logical consequence of this mechanism of micelle formation. If the earliest molecules of life are also trapped within the developing aqueous core, then they should be free to interact and adapt along with the micelle.

The final micelle structure therefore, could consist of hydrophobic groups extending towards the center of the structure, but remaining partially turned upon themselves at their ends as illustrated in Figure 2E.

When one envisions a finished micelle, it is natural to accept the long chain on one segment of the arc of the sphere extending into the center and held there by hydrophobic interactions with the opposite number on the other side of the sphere, as well as those adjacent to it. This finished sphere seems to preclude the possibility of an aqueous core.

But if a micelle develops in time in the manner described in this article, the chains added tend to avoid the aqueous center and dissolve into one another on that side of the micelle. Only when the sphere is half completed, do incoming fatty acids have chains on the opposite side to extend up to. In this instance, the length of the chain may also determine the size of the sphere from the very outset of micelle development.

The last incoming sub units may encounter a greater charge density at the point of entry, and the charged heads may nestle into the envelope allowing the hydrophobic tails to snake into the oily interior.

It would seem that fatty acid chains synthesized at random would be of different chain lengths. It seems logical to assume therefore, that the longest chains would determine the size of the sphere, leaving potential space for water where the short chain ends. If we imagine a 20 carbon chain alternating with a 12 carbon chain fatty acid, the space vacated by the 8 missing methylene groups ( -CH2- ) in the short chain could provide space in which water might be trapped during the development of the micelle.

So a developing micelle could have two sources of trapped water, namely, that in the central core and the water that was not excluded by short chain fatty acids.

Alternately, if this micelle model does not conform to any model that can be constructed from the experimental data, then we may simply have to resort to the option that the original biotic structure may simply have been a cell bounded by a membrane consisting of two phospholipid layers arranged the way they are in modern cells with the charged heads oriented towards the inner and outer aqueous media. This would obviate the need to postulate the existence of a micelle with an aqueous core as the original biotic entity.

Summary:If one views the micelle as a developing entity, starting with the first

few fatty acids that make up the first arc of the sphere, then it is possible to illustrate a developing micelle that can include a small aqueous part that becomes trapped within its developing borders.

But even if the proposed mechanism of arc growth turns out to be true, this is not a guarantee that an aqueous core will necessarily be trapped within the completed sphere. This process could also result in a finished sphere in which an aqueous phase was not included, whereby the last incoming sub units simply positioned themselves in such a way as to exclude the last vestiges of remaining water.

If this is the case, and water is completely excluded from the finished micelle, then this would rule out the micelle as the original biotic entity from which cells evolved, but the mechanism of growth from small to larger arcs is still a logical one.

Acknowledgements:Thanks to Lisa Rhoads, secretary of the Science Department, for

Retracing the micelle illustrations from my originals.

References:

Deduve, Christian. Blueprint of a cell: an essay on the nature and origin of life. Burlington, NC: Neil Patterson Publishers: (1991)

Gauthier, Peter. Origins: Speculations about the Spontaneous Generation of the first Biotic Structure. BIOS Vol. 65 No. 4 (1995)

Weber, Arthur L. The triose model: glyceraldehyde as a source of energy and Monomers for prebiotic condensation reactions. Origins of Life & Evolution of the Biosphere 17:107-119; (1987)

Micelle Formation – From Small Spheres to Large Spheres.

By

Peter Gauthier

Peter Gauthier, Ph.D. Email: peterspond@roadrunner.comDept. Science (retired)Mount Saint Mary’s CollegeEmmitsburg, MD 21727

Micelle Formation – From Small Spheres to Large Spheres.

Abstract

This article argues against the notion that micelles can grow from complete, small spheres into larger spheres by the accretion of fatty acid sub units. The major objection to this mechanism lies in the fact that a substantial aqueous core would seem to result from this type of growth. At some point in this section, a reference is made to the first article comparing the small aqueous phase which could result from arc formation in Gauthier’s article, to the large aqueous phase which would necessarily result from the growth of large spheres from small ones as depicted in this article.

Micelle Formation – From Small Spheres to Large Spheres.

Another mechanism of micelle development could involve the growth of large spheres from small ones. But can fully formed small spheres give rise to larger spheres by the accretion of micellar sub units which penetrate the outer envelope of the growing sphere?

According to this hypothesis a small micelle would develop into a larger one as illustrated below in Figure 1.

Figure 1.

*

*Represents the process whereby sub units of fatty acids penetrate the outer envelope of the growing sphere, and bring about this increase in mass and volume to form the larger sphere.

If micelle growth occurs in this way, i.e. large micelles developing from smaller ones by the addition of sub units, then the following diagram would roughly represent the process. Illustrated below in is a cross-section of the fully formed small sphere with hydrophobic tails reaching to the center, and the finished large sphere with hydrophobic tails extended maximally, leaving a large aqueous center. As the sphere grows, the tips of the hydrophobic tails would find themselves further and further from the center of the growing sphere as illustrated in Figure 2.

Figure 2.

For clarity of representation only four sub units are shown in the small sphere, and eight sub units are shown in the finished sphere. In addition, all micellar sub units are identical in chain length and are shown as straight lines.

Legend:

Hydrophilic Head:

Hydrophobic Tail: _____

This article presents arguments against the growth of micelles from smaller, fully formed micelles by the addition of sub units as illustrated in Figure 2.

Arguments against the growth of micelles from smaller, fully formed spheres.

1. If one assumes that the hydrophobic portion of the sub units extends to the center of the fully formed small sphere, then the growth of this sphere by the addition of sub units should result in the larger sphere shown in Figure 2. As the sphere grows in size with the addition of new units, the chains (of equal length in this case) can no longer extend to the center of the sphere, thus leaving an open core which grows larger with each additional sub unit added to the sphere. But this model does not conform to the current perception of the finished micelle, in which the chains extend to the center of the sphere. Although Gauthier’s model of the finished micelle provides for a small aqueous core, it doesn’t compare to the large aqueous center of a micelle that would result from a sphere which developed according to the mechanism illustrated here, whereby complete small spheres grow into larger spheres by the addition of sub units. But the core of the micelle is non polar which would seem to discredit this hypothesis of micellar growth.

2. If a small sphere develops into a larger sphere by the accretion of sub units, then what is the force driving that development. Long hydrophobic chains must penetrate a dense hydrophilic outer membrane which envelops the small complete sphere. But what drives these hydrophobic chains to penetrate this layer, when they can more easily dissolve into one another to form a micelle according to Gauthier’s mechanism?

If small spheres formed spontaneously, it seems that the outer hydrophilic environment would naturally repel incoming hydrophobic chains from penetrating the membrane, and preclude growth of these small spheres into larger ones by this mechanism. If the envelope of the small sphere is uneven and filled with gaps, then it is possible to imagine that a hydrophobic tail could penetrate the envelope in that part of the membrane where the charge density has been reduced. Also polar heads could be displaced by upheavals of the inner hydrophobic tails which might also provide an avenue of entrance for incoming non polar tails, but this seems a less compelling explanation than that presented in the article.

The argument can be made that an incoming sub unit is so positioned that the hydrophilic head nestles into the charged envelope of a small, complete sphere, resulting in sufficient perturbation at the surface and in the underlying chains to briefly provide an avenue of entrance for the sub unit as adjoining non polar groups dissolve into one another. Then the long tail could snake its way into the interior of the sphere dissolving into the oily matrix as it moves in. This is the mechanism proposed by Gauthier for the incorporation of the last sub units that finish the sphere. But incorporation of sub units into growing arcs in the manner described in the article seems a more likely way in which spheres would tend to grow.

But this last mechanism of micelle growth does not contradict Gauthier’s hypothesis; it is simply a variation on the theme that was presented. The only difference is that in Gauthier’s model we are not dealing with finished spheres, but with portions, or arcs of spheres, until the final incoming sub-units nestle in and complete the micelle.

3. A last point should be made regarding this matter. To accept the existence of small spheres a priori, seems to beg the question: How did the small spheres come into existence in the first place? To simply say that small spheres give rise to large spheres by the accretion of sub units doesn’t establish how the sub units originally came together to form the small sphere, and that is the point of departure of Gauthier’s article.

4. If the growth of a large sphere from a small one occurs as illustrated in Figure 2, then it would seem that micelles could not grow in this fashion since the center of the micelle consists of non polar material, and not of a large aqueous center. So even if one accepts the notion that the polar head could nestle into the charged envelope, this would still be ruled out as a possible mechanism of micellar growth.

References:

Gauthier, P. Micelle Formation – From Arc to Sphere. Unpublished.