The circadian rhythm is generated at the cellular level by a molecular clock system that involves specific genes. Studies have revealed that circadian clock disruption is a control point in cancer progression. Colorectal cancer (CRC) is one of the cancers closely associated with circadian disruption. In the present review, the involvement of the circadian clock in CRC development was summarized. Abnormal expression of certain clock genes has been found in patients with CRC and their correlation with clinicopathological features has also been explored. The period and cryptochrome 2 (Cry2), Sirtuin1 (SIRT1) and neuronal PAS domain protein 2 (NPAS2) genes were reported to have tumour suppressor properties. Conversely, Cry1, brain and muscle ARNT‑like‑1, circadian locomotor output cycles kaput (CLOCK) and timeless may aggravate CRC progression, but these findings are not consistent and require to be confirmed by further research. Circadian scheduling also indicated advantages in chemotherapy treatments for patients with CRC by increasing the maximum tolerated doses and decreasing toxicities. Dysfunction of the molecular CLOCK system disrupted cellular processes to accelerate colon tumorigenesis, such as metabolism, cell cycle, DNA damage repair, proliferation and apoptosis, epithelial‑mesenchymal transition and stemness. The clock gene network and how the dynamics of the system influence CRC were discussed.

Microalgae are important renewable feedstock to produce biodiesel and high-value chemicals. Different wavelengths of light influence the growth and metabolic activities of algae. Recent research has identified the light-sensing proteins called photoreceptors that respond to blue or red light. Structural elucidations of algal photoreceptors have gained momentum over recent years. These include channelrhodopsins, PHOT proteins, animal-like cryptochromes, and blue-light sensors utilizing flavin-adenine dinucleotide proteins. Pulsing light has also been investigated as a means to optimize energy inputs into bioreactors. This study summarizes the current structural and functional basis of photoreceptor modulation to optimize the growth, production of carotenoids and other high-value metabolites from microalgae. The review also encompasses novel photobioreactor designs that implement different light regimes including light wavelengths and time to optimize algal growth and desired metabolite profiles for high-value products.

Cyclobutane pyrimidine dimer (CPD) photolyase (PL) is a structure-specific DNA repair enzyme that uses blue light to repair CPD on DNA. Cryptochrome (CRY) DASH enzymes use blue light for the repair of CPD lesions on single-stranded (ss) DNA, although some may also repair these lesions on double-stranded (ds) DNA. In addition, CRY DASH may be involved in blue light signaling, similar to cryptochromes. The focus of this review is on spectroscopic and biophysical-chemical experiments of the enzyme-substrate complex that have contributed to a more detailed understanding of all the aspects of the CPD repair mechanism of CPD photolyase and CRY DASH. This will be performed in the backdrop of the available X-ray crystal structures of these enzymes bound to a CPD-like lesion. These structures helped to confirm conclusions that were drawn earlier from spectroscopic and biophysical-chemical experiments, and they have a critical function as a framework to design new experiments and to interpret new experimental data. This review will show the important synergy between X-ray crystallography and spectroscopic/biophysical-chemical investigations that is essential to obtain a sufficiently detailed picture of the overall mechanism of CPD photolyases and CRY DASH proteins.

Currently at least two independent systems of magnetoreception are believed to exist in birds, based on different biophysical principles, located in different parts of their bodies, and having different innervation. One magnetoreceptory system is located in the retina and may be based on photo-induced biradical chemical reactions on the basis of cryptochrome. Information from these receptors is processed in a specialized part of visual Wulst, the so-called Cluster N. There are good reasons to believe that this visual magnetoreceptor processes compass magnetic information which is necessary for migratory orientation. The second magnetoreceptory system is probably iron-based (biogenic magnetite), is located somewhere in the upper beak (its exact location and ultrastructure of receptors remain unknown), and is innervated by the ophthalmic branch of trigeminal nerve. It cannot be ruled out that this system participates in spatial representation and helps forming either a kind of map or more primitive signposts, based on regular spatial variation of the geomagnetic field. The magnetic map probably governs navigation of migrating birds across hundreds and thousands of kilometers. Apart from these two systems whose existence may be considered to be convincingly shown (even if their details are not yet fully clear), there are data on the existence of magnetoreceptors based on the vestibular system. It cannot be ruled out that iron-based magnetoreception takes place in lagena (a structure homologous to cochlea of marsupials and eutherians), and the information perceived is processes in vestibular nuclei. The very existence of this magnetoreception system needs verification, and its function remains completely open.

OBJECTIVE: Experimental studies have shown that some circadian core clock genes may act as tumour suppressors and have an important role in the response to oncological treatment. This study investigated the evidence regarding modified expression of core clock genes in colorectal cancer and its correlation to clinicopathological features and survival.
METHODS: A systematic review was conducted without meta-analysis according to the PRISMA guidelines on 24 March 2014 using PubMed and EMBASE. Eligibility criteria were: study design, original research article, English language, human subjects and gene expression of colorectal cancer cells compared with healthy mucosa cells from specimens analysed by real-time or quantitative real-time polymer chain reaction. The expression of the core clock genes Period, Cryptochrome, Bmal1 and Clock in colorectal tumours were compared with healthy mucosa and correlated with clinicopathological features and survival.
RESULTS: Seventy-four articles were identified and 11 studies were included. Overall, gene expression of Period was significantly decreased in colorectal cancer cells compared with healthy mucosa cells. This tendency was also seen in the gene expression of Clock. Other core clock genes did not appear to be differentially expressed. Decreased Period gene expression was correlated to some clinicopathological features.
CONCLUSIONS: The Period genes seemed to be modified in colorectal tumour cells compared with normal mucosa. Core clock genes might be possible future biomarkers in colorectal cancer.

Six well-characterized photoreceptor families function in Nature to mediate light-induced signal transduction: the rhodopsins, phytochromes, xanthopsins, cryptochromes, phototropins, and BLUF proteins. The first three catalyze E/Z isomerization of retinal, phytochromobilin, and p-coumaric acid, respectively, while the last three all have a different flavin-based photochemistry. For many of these photoreceptor proteins, (many of) the details of the conversion of the light-induced change in configuration of their chromophore into a signaling state and eventually a biological response have been resolved. Some members of the rhodopsins, the xanthopsins, and the phototropins are so well characterized that they function as model systems to study (receptor) protein dynamics and (un)folding.