Cluster hypothesis

In the hypothesis, Points 5 and 8 above (alternative structures) have come under criticism, first by Skovborg et al. (1992) and then by Natarajan et al. (1994). However, Skovborg noted that alternating structures may account for some of his nucleation data. A further criticism of the labile cluster hypothesis is that the energy barrier for agglomeration of clusters is far larger than cluster disintegration (Radhakrishnan and Trout, 2002). 

Fig. 5.11. Acid-base cluster hypothesis. The cluster of acidic residues and basic residue is indicated on the upper portion of the figure. Fq is located on the left side where FT flux is transferred to the cluster. The movement of three protons from three NHj to three COO results in the charge neutralization, which causes conformational change to release tightly bound A, /S, y bidentate ATP-Mg complexes. After the energy is used up, three COOH s are dissociated and protons are released into the matrix side because of their pAT. Three NHj are protonated from the Fq side. The formation of ATP takes place without added energy, via in-line nucleophilic substitution (SNj) of O" of ADP to the P of inorganic phosphate. For details, refer to the text.

Acid base cluster hypothesis in proton motive ATP synthesis... 

We find that the nucleation proceeds via "the local structuring mechanism/ " i.e., a thermal fluctuation causing the local ordering of CO2 molecules leads to the nucleation of the clathrate, and not by the labile cluster hypothesis, one current conceptual picture. The local ordering of the guest molecules induces ordering of the host molecules at the nearest- and next-to-nearest-neighbor shells, which are captured by a three-body host-host order parameter, f these thermodynamic fluctuations lead to the formation of the critical nucleus. 

Conclusion arid Discussion—As the results of the present experiment exhibit no deviation from the law Up = constant it follows that both the positive and the negative ions did not disintegrate at the potentials employed. It may be seen from the tables that the values of X/p were very close to the values at which sparking would occur in the respective gases. And since the cluster hypothesis demands the disintegration of the ions when the values of X/p are much lower than those employed,15 it therefore follows that these results are directly contradictory to this hypothesis. 

There remains, however, an experimental fact which the cluster hypothesis seems to be able to explain better than the small-ion hypothesis, and that is the difference between the mobilities of the positive and the negative ions. For, if both the positive and the negative ions are single molecules carrying elementary charges different only in signs, why should they have different mobilities Whereas if the ions are clusters the difference in their mobilities may be ascribed to the difference between the numbers of molecules constituting the two kinds of ions. 

To test our hypothesis we used a non-hierarchical cluster procedure, which mostly includes partitioning methods that create disjunctive clusters. Initial clusters were made by giving the number of the future groups, which was based on the hierarchical cluster method described above. We then tested our hypotheses concerning the number of clusters (Hypothesis I) and the role of employed variables (concerning specific investments, bargaining power and contract determination. Hypothesis II). 

Similar MC calculations were used by Trout s group to study the carbon dioxide-liquid water interface at 220 K and 4 MPa near the phase boundary of a carbon dioxide hydrate (273 K and 4MPa). Nucleation was achieved by seeding the system with a cluster of carbon dioxide hydrate. It was found that a small cluster with diameter <9.6 A dissolved into the solution readily. A hydrate crystal started to grow, however, when a hydrate cluster twice that size (19.3 A) was implanted into the system. The crystal eventually spanned the whole system (Figure 22). Thus the critical nucleus size for hydrate nucleation is estimated to be about 19 A consisting of approximately 200 water molecules. This is a considerably smaller number than that estimated from the local harmonic model of around 600 molecules. The theoretical results refuted the labile cluster hypothesis.This hypothesis speculates the agglomeration... 

In unsupervised learning, the outcome is usually a hypothesis to then be tested, often usiag classification or prediction methods. If the unsupervised learning process suggests the presence of distinct clusters, the hypothesis can be tested by applyiag a classification method to the data. A low number of misclassified samples would tend to reinforce the hypothesis. 

This review presents an overview of the discovery of the Fepr protein, the spectroscopy that led to the suggestion that it contained a [6Fe-6S] cluster, and the subsequent crystal structure analysis that disproved this hypothesis, yet uncovered what is at a present a unique Fe-S cluster in biology. 

These two redox-linked protons were tentatively attributed to the N -protons of the cluster-ligating histidine residues (130, 131, 137). Although this attribution appears likely in the light of the structure, so far no experimental evidence substantiating this hypothesis is available. 

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