Retinal guanylate cyclases 1 and 2 (GC1 and GC2) are responsible for synthesis of cyclic GMP in rods and cones, but their individual contributions to phototransduction are unknown. We report here that the deletion of both GC1 and GC2 rendered rod and cone photoreceptors nonfunctional and unstable. In the rod outer segments of GC double knock-out mice, guanylate cyclase-activating proteins 1 and 2, and cyclic GMP phosphodiesterase were undetectable, although rhodopsin and transducin ␣-subunit were mostly unaffected. Outer segment membranes of GC1 ؊/؊ and GC double knock-out cones were destabilized and devoid of cone transducin (␣-and ␥-subunits), cone phosphodiesterase, and G protein-coupled receptor kinase 1, whereas cone pigments were present at reduced levels. Real time reverse transcription-PCR analyses demonstrated normal RNA transcript levels for the downregulated proteins, indicating that down-regulation is posttranslational. We interpret these results to demonstrate an intrinsic requirement of GCs for stability and/or transport of a set of membrane-associated phototransduction proteins.

Vision begins with photoisomerization of visual pigments. Thermal energy can complement photon energy to drive photoisomerization, but it also triggers spontaneous pigment activation as noise that interferes with light detection. For half a century, the mechanism underlying this dark noise has remained controversial. We report here a quantitative relation between a pigment’s photoactivation energy and its peak-absorption wavelength, λmax. Using this relation and assuming that pigment activations by light and heat go through the same ground-state isomerization energy barrier, we can predict the relative noise of diverse pigments with multi–vibrational-mode thermal statistics. The agreement between predictions and our measurements strongly suggests that pigment noise arises from canonical isomerization. The predicted high noise for pigments with λmax in the infrared presumably explains why they apparently do not exist in nature.

The reduced graphene oxide (RGO)/Fe 3 O 4 composites with an obviously enhanced microwave absorption property had been successfully fabricated by rational one-pot simplified co-precipitation route, which avoided the usage of inert gas and any additional chemical agents (such as surfactants and stabilizer).Given these advantages, the strategy described in this study can be developed as a simple and large-scale yield route to RGO/Fe 3 O 4 composites. The morphology, structure, thermal stability, magnetic and microwave electromagnetic properties of as-prepared composites were characterized by XRD, XPS, TEM, FT-IR, Raman, TG and VSM. Those composites exhibit excellent microwave absorption properties, which are attributed to effective complementarities between the dielectric loss and the magnetic loss. The microwave absorption mechanism of the RGO/Fe 3 O 4 composites was studied in detail. For RGO/Fe 3 O 4 -3 composite, the maximum R L reaches -44.6 dB at 6.6 GHz with a thickness of 3.9 mm, and the bandwidth of RL less than -10 dB can reach up to 4.3 GHz (from 12.2 to 16.5 GHz) with a thickness of 2.0 mm. Moreover, the microwave absorption property can be tuned easily by varying the (RGO)/(Fe 3 O 4 ) ratio and layer thickness of the samples. It is believed that such composites will find their wide applications in microwave absorbing area.-2 -expanded EM interference problems. 3-5 They can absorb microwaves effectively and convert EM energy into thermal energy or make microwaves dissipated by interference. The microwave absorbing materials are now requested to have strong absorption characteristics, wide absorption frequency, lightweight and antioxidation. 4 There are a number of microwave absorbing materials such as ferrites, carbonyl iron, conducting polymers and carbon-based materials etc. 6-9 However, the traditional microwave absorbing materials can not meet all of the requirements such as strong, wide, lightweight and thin at the same time.Hence, extensive studies have been made to develop novel microwave absorping materials with high absorption and wide absorption frequency.Graphene, a novel carbon nanomaterial consisting of one-atom-thick, hexagonally arranged carbon atoms, has attracted extensive attention owing to its superior electronic, thermal and mechanical properties as well as its chemical stability. 10,11 Due to its special surface properties and layered structure, graphene becomes potential nanoscale building blocks for new hybrid materials. 12 Recent research shows that inorganic nanoparticles, such as Au, Ag, Fe 3 O 4 and Co 3 O 4 , etc., could be attached to graphene or graphene oxide (GO) to form hybrid materials, which have potential applications in surface enhanced Raman scattering (SERS), lithium ion batteries, hydrogen storage, microwave absorption and magnetic resonance imaging (MRI) contrast agent, etc.. [13][14][15][16] As a class of promising microwave absorping materials, carbon-based materials exhibited several exceptional properties including lightweight, wide absorption frequency, high...