The ability to temporally and spatially control the function of peptides/proteins by a stimulus has received increased attention due to its potential in various fields such as chemical biology and drug delivery. Recently, photo-induced processing (peptide bond cleavage) or conformational change has been successfully applied to convert inactive (or active) peptides and proteins into their corresponding active (or inactive) forms at a desired time and location. [1a-i] Increasing the diversity of the trigger that is involved in a processing reaction might facilitate stimulus-responsive processing to become a general method for controlling peptide functions. Therefore, we attempted to design an amino acid derivative that induces a processing reaction as a response to a wide variety of stimuli. Inspired by the trimethyl lock system, [2,3] we designed stimulus-responsive peptide 1, which can release a functional peptide after the stimulus-induced removal of a phenolic protective group (PG) and subsequent processing reaction (Scheme 1). Peptide 1 features the nucleophilic involvement of a regenerated phenolic hydroxyl group to an adjacent peptide bond to release functional peptides. In this investigation, we chose a photo-removable o-nitrobenzyl (o-NB) and a phosphat-A C H T U N G T R E N N U N G ase-removable phosphate group for phenolic protection to afford stimulus-responsive model peptides.Scheme 2 shows the synthesis for photo-responsive model peptide 8. Aldehyde 2[2] was a-aminated with di-tert-butyl azodicarboxylate in the presence of pyrrolidine. After reduction of the aldehyde group with sodium borohydride, the resulting alcohol was protected with a tert-butyldimethylsilyl (TBS) group to give silyl ether 3. Trifluoroacetylation of the terminal nitrogen in 3 with trifluoroacetic anhydride (TFAA) and subsequent NÀN bond cleavage by sammarium(II) iodide in the presence of hexamethylphosphoramide (HMPA) and tert-butanol gave amino alcohol 4. The benzyl group on 4 was removed by hydrogenolysis and the generated phenolic hydroxyl group was protected with an o-nitrobenzyl group to afford o-NB ether 5. After removing the TBS group of 5 under acidic conditions, a two-step oxidation was performed to give carboxylic acid 6. The tert-butyloxycarbonyl (Boc) group on 6 was removed with hydrogen chloride in ethyl acetate to yield an amine, which was reprotected with a fluorenylmethoxycarbonyl (Fmoc) group to give Fmoc-protected photo-responsive processing device 7. The total yield of Fmoc derivative 7 was 11 % over 12 steps from aldehyde 2. Finally, the incorporation of amino acid 7 into the peptide by standard Fmoc solid-phase peptide synthesis (SPPS) afforded photo-responsive model peptide 8 as a diastereomeric mixture.To examine the photoreactivity of model peptide 8, we performed the photo-processing reaction that is outlined in Scheme 1. Design of a stimulus-responsive peptide.Scheme 2. Reagents and conditions. a) di-tert-butyl azodicarboxylate, pyrrolidine, CH 2 Cl 2 , 85 %; b) NaBH 4 , MeOH, 100

The role of light for the low-pH-induced root hair formation process in lettuce seedlings was reported. A high rate of root hair formation was induced by low-pH (pH4.0) treatment under continuous white light, while no root hairs were observed in the dark irrespective of pH conditions. The fluence requirement for root hair initiation was lower than that for root hair elongation, indicating that two different mechanisms operate in the photoinduction of mature root hairs. With regard to root hair initiation, red and blue light were equally effective, even more than white light, while l i e initiation was obtained with far-red light. The fluence response curve for red and blue light was biphasic and showed two maxima at about 100 and 1,OOO Jm2. The inductive effect of 100 J m 2 red light could be partially reversed by subsequent far-red light only one time. On the other hand, the inductive effect of 1,OOO Jm-* red liht was partially reversed by subsequent far-red light irradiation at least twice. These results indicate the involvement of phytochrome in this response. The inductive effect of blue light was repeatedly reversed by subsequent far-red light irradiation, suggesting that the blue-light induction was mainly mediated by phytochrome.

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