## 4 Discussion and Conclusions  
Initiation and control of stem cell differentiation into osteoblasts is of particular interest for bone regeneration, bone healing and bone transplantation. As it has been shown that the population  
Figure 8: RRM cross-spectrum of parathyroid hormone proteins, parathyroid hormone receptor1 proteins and SDF-1\(\alpha\) proteins. The more prominent common characteristic frequency for these proteins is at f3 = 0.3975 \(\pm\) 0.0108, which represents an electromagnetic radiation wavelength of about 502 nm, while the less prominent frequency is at f2 = 0.1885 \(\pm\) 0.0108, which represents an electromagnetic radiation wavelength of about 1066 nm. Figure 7: RRM cross-spectrum of parathyroid hormone proteins and SDF-1\(\alpha\) proteins. The prominent common characteristic frequency for these proteins is also f3 = 0.3975 \(\pm\) 0.0108, which represents an electromagnetic radiation wavelength of about 502 nm. of pluripotent stem cells highly express parathyroid hormone type 1 receptors, it was postulated that parathyroid hormone has a similar action as SDF-1\(\alpha\) in control of stem cells differentiation [2]. Moreover, it has been shown that the PhotoBioModulation (PBM) of specific blue and green light electromagnetic wavelengths encourage osteoblastic differentiation of human adipose-derived stem cells [3]. Here, we hypothesised that stimulation of osteoblast differentiation by specific blue and green light wavelengths (frequencies) is related to activation of proteins involved in osteoblast differentiation like PTH and SDF-1\(\alpha\). For this purpose, we have utilised Resonant Recognition Model (RRM), which proposes that protein activation and function are based on specific wavelengths (frequencies) of electromagnetic radiation within ultra-violet, visible, infra-red and far infra-red light. Thus, by using the RRM model, we have analysed parathyroid hormones and related proteins with the purpose to predict wavelengths (frequencies) that characterise parathyroid hormone activities, particularly differentiation of stem cells into osteoblasts. It can be observed from the results above that there are two important characteristic frequencies (wavelengths) for the activity of parathyroid hormone (PTH), namely parathyroid hormone receptor1 and stromal cell-derived factor-1 (SDF-1\(\alpha\)). These frequencies (wavelengths) are f1/f3 = 0.3975 \(\pm\) 0.0108 (502 nm) and f2 = 0.1885 \(\pm\) 0.0108 (1066 nm). According to all above results, the frequency f2 = 0.1885 \(\pm\) 0.0108 represents parathyroid hormone recognition/interaction with parathyroid hormone receptor1, while the frequency f1/f3 = 0.3975 \(\pm\) 0.0108 represents the common function of parathyroid hormone and stromal cell-derived factor-1, which is the stem cell differentiation function. It is important to observe that a wavelength of 502 nm related to frequency f1/f3 is exactly between the wavelengths of 420 nm and 540 nm, which in a previous experiment was found to be effective in stimulating osteoblast differentiation [3]. This indicates that specificity of wavelengths (frequencies), which stimulate osteoblast differentiation, could be explained by photo activation of proteins involved in osteoblast differentiation, as predicted by the RRM model. Even more, as the RRM model predicts that the most effective wavelength would be 502 nm, which is in between the already tested wavelengths of 420 nm and 540 nm [3], we propose that a wavelength of 502 nm would induce even more efficient stimulation of osteoblast differentiation. Thus, the findings of this research can be used in development of improved techniques for differentiation of stem cells using the electromagnetic radiation of a specific wavelength of 502 nm. Future research should involve validation of these results by experimental testing of stem cell differentiation.