Mic selection, nor HLA restriction, but rather is a result of recombinatorial usage bias, or ranking of various segments. Figure 4 demonstrates this phenomenon, and it is also reflected in the power law distribution of the final T-cell clonal distribution observed. The relationship between TCR locus organization and segment selection in this rearrangement process and its impact on the T-cell repertoire generation has been a focus of intensive study in the recent years. Recently, a biophysical model describing yeast chromosome conformation has been applied to the murine TCR b-D and -J segment and the derived model based on `genomic distance’ between these order Talmapimod segments has partially recapitulated the observed bias in J segment usage [36]. This supports the notion that chromatin conformation, and TCR spatial organization has a formative role in the T-cell repertoire generation. Regardless of the mechanism of recombination, it has become obvious that the T-cell repertoire that emerges has a `biased’ VDJ segment usage, with certain segments being used more frequently than others. This suggests that these segments may be more efficiently rearranged resulting in their over representation in the repertoire and vice versa. The effect of spatial organization of TCR gene segments on recombination frequency is also evident when modelling the rearrangement likelihood in the murine TRA taking into account the SCIO-469 web relative positioning of V and J segments [37]. Assuming sequential availability of V and J segments to recombine with each other in a time-dependent process, it was demonstrated that the proximal, central and distal J segments had a greater likelihood of recombining with the correspondingly positioned V segments. The model output demonstrates a `wavefront’ of recombination probability propagating through each of the regions when individual J segments were analysed for their ability to recombine with the V segments and vice versa. A similar model examined the recombination probabilities as a function of the size of the `window’ of the TRA-V and -J regions available, putting forth the notion that sequential availability of individual gene segments determines the recombination frequencies [38]. These models reinforce the deterministic aspect of the TCR locus recombination and highlight the importance of the scaling observations we report in this paper. Given the emergence of the constant p in the equations describing the fractal nature of the T-cell repertoire in normal stem cell donors and the periodic nature of TCR gene segments on the TCR locus, their relative positions were examined using trigonometric functions to account for the helical nature of DNA. Similarity was observed in the relative location of the V, D and J segments across the TRA and TRB loci when they were examined using logarithmic scaling, with increasingly complex waveforms observed as higher-order harmonics were evaluated (data not shown). There are several important implications of this observation. First, analogous to the phenomenon of superposition (constructive or destructive interference) observed in the mechanical and electromagnetic waves, one may consider that relative position of a particular segment, reflected by the coordinates on the DNA helix (estimated by the sine and cosine functions, and angular distancersif.royalsocietypublishing.org J. R. Soc. Interface 13:V 1 2 2 3Jrsif.royalsocietypublishing.org1.0 0.5 5?0 3?J. R. Soc. Interface 13:3?5?Figure 5. A model depicti.Mic selection, nor HLA restriction, but rather is a result of recombinatorial usage bias, or ranking of various segments. Figure 4 demonstrates this phenomenon, and it is also reflected in the power law distribution of the final T-cell clonal distribution observed. The relationship between TCR locus organization and segment selection in this rearrangement process and its impact on the T-cell repertoire generation has been a focus of intensive study in the recent years. Recently, a biophysical model describing yeast chromosome conformation has been applied to the murine TCR b-D and -J segment and the derived model based on `genomic distance’ between these segments has partially recapitulated the observed bias in J segment usage [36]. This supports the notion that chromatin conformation, and TCR spatial organization has a formative role in the T-cell repertoire generation. Regardless of the mechanism of recombination, it has become obvious that the T-cell repertoire that emerges has a `biased’ VDJ segment usage, with certain segments being used more frequently than others. This suggests that these segments may be more efficiently rearranged resulting in their over representation in the repertoire and vice versa. The effect of spatial organization of TCR gene segments on recombination frequency is also evident when modelling the rearrangement likelihood in the murine TRA taking into account the relative positioning of V and J segments [37]. Assuming sequential availability of V and J segments to recombine with each other in a time-dependent process, it was demonstrated that the proximal, central and distal J segments had a greater likelihood of recombining with the correspondingly positioned V segments. The model output demonstrates a `wavefront’ of recombination probability propagating through each of the regions when individual J segments were analysed for their ability to recombine with the V segments and vice versa. A similar model examined the recombination probabilities as a function of the size of the `window’ of the TRA-V and -J regions available, putting forth the notion that sequential availability of individual gene segments determines the recombination frequencies [38]. These models reinforce the deterministic aspect of the TCR locus recombination and highlight the importance of the scaling observations we report in this paper. Given the emergence of the constant p in the equations describing the fractal nature of the T-cell repertoire in normal stem cell donors and the periodic nature of TCR gene segments on the TCR locus, their relative positions were examined using trigonometric functions to account for the helical nature of DNA. Similarity was observed in the relative location of the V, D and J segments across the TRA and TRB loci when they were examined using logarithmic scaling, with increasingly complex waveforms observed as higher-order harmonics were evaluated (data not shown). There are several important implications of this observation. First, analogous to the phenomenon of superposition (constructive or destructive interference) observed in the mechanical and electromagnetic waves, one may consider that relative position of a particular segment, reflected by the coordinates on the DNA helix (estimated by the sine and cosine functions, and angular distancersif.royalsocietypublishing.org J. R. Soc. Interface 13:V 1 2 2 3Jrsif.royalsocietypublishing.org1.0 0.5 5?0 3?J. R. Soc. Interface 13:3?5?Figure 5. A model depicti.