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When thyroxine, in the absence of serum, is submitted to electrophoresis on filter paper in barbiturate buffer at pH 8-6, all the thyroxine remains at the origin. If, however, the electrophoresis is carried out on filter paper that has been soaked in phenylalanine, or if phenylalanine is added to the paper with the thyroxine, the thyroxine moves towards the anode at a speed between that of the ocl-and OC2-globulins of human serum (Myant & Osorio, 1960). The term 'phenylalanine effect' was suggested for this action of phenylalanine, and for that of any other substance that exerts the same effect on the electrophoretic mobility of thyroxine on paper. The cause of the phenylalanine effect is unknown. We suggested, however, that it might be due to blocking of thyroxine-binding sites on the filter paper, which normally prevent thyroxine from moving towards the anode.It has recently been shown (Ingbar, 1958) that when radioactive thyroxine, in the presence of human serum, is submitted to paper electrophoresis in tris-maleate buffer at pH 8-6, most of the activity is distributed between two peaks, one at the inter-alpha zone and the other in front of the albumin band (pre-albumin zone). Our observations with barbiturate buffer raised the question as to whether the phenylalanine effect also occurs in the presence of tris-maleate buffer and, if so, how far it could account for Ingbar's observations. We have therefore studied the effect of phenylalanine on the electrophoretic mobility of thyroxine in tris-maleate buffer at different hydrogen-ion concentrations with and without human serum. Observations were also made on the partition of thyroxine between the inter-alpha and pre-albumin zones at different concentrations of thyroxine. In an attempt to explain why thyroxine does not move to the pre-albumin zone in the presence of serum in barbiturate buffer, observations were made on the movement of thyroxine on paper electrophoresis in two dimensions.

Membrane tension plays an inhibitory role in clathrin-mediated endocytosis (CME) by impeding the transition of flat plasma membrane to hemispherical clathrin-coated structures (CCSs). Membrane tension also impedes the transition of hemispherical domes to omega-shaped CCSs. However, CME is not completely halted in cells under high tension conditions. Here we find that epsin, a membrane bending protein which inserts its N-terminus H0 helix into lipid bilayer, supports flat-to-dome transition of a CCS and stabilizes its curvature at high tension. This discovery is supported by molecular dynamic simulation of the epsin N-terminal homology (ENTH) domain that becomes more structured when embedded in a lipid bilayer. In addition, epsin has an intrinsically disordered protein (IDP) C-terminus domain which induces membrane curvature via steric repulsion. Insertion of H0 helix into lipid bilayer is not sufficient for stable epsin recruitment. Epsin’s binding to adaptor protein 2 and clathrin is critical for epsin’s association with CCSs under high tension conditions, supporting the importance of multivalent interactions in CCSs. Together, our results support a model where the ENTH and unstructured IDP region of epsin have complementary roles to ensure CME initiation and CCS maturation are unimpeded under high tension environments.

It has been suggested that lack of thyroid hormone during foetal life contributes to the mal-development of the brains of cretinous infants. It has not been easy to get direct evidence for this view, not only because of the difficulty of obtaining brain tissue from cretins, but also because cretinism is hardly ever diagnosed before the infant is several weeks old. There is, however, some evidence that in cretinism due to congenital aplasia of the thyroid the brain is histologically abnormal at or near the time of birth (Wilkins, 1957).The possibility that thyroid hormone may be necessary for normal development of the mammalian brain in utero, as well as during postnatal life, led us to study the effect of thyroid deficiency on the growth of the brain in rabbits during the later stages of foetal life and the first few days after birth. Our results are described in this paper.It seemed possible that if thyroid deficiency in utero was found to influence the development of the brain, this might be due to interference with the synthesis of some essential constituent of the brain. We have therefore begun a study of the deposition of phospholipid in the developing brains of normal and thyroid-deficient rabbits. Preliminary results of this work are included here. METHODSAll the rabbits used for analysis of phospholipid in the brain were of the Dutch strain. In addition to these, a few rabbits of mixed strain were included for the observations on body weight and brain weight. The animals were given a diet of dried pellets (M.R.C. Diet No. 18, described by Bruce & Parkes, 1946). Methyl-thiouracil was given from the 10th day of pregnancy until the end of the experiment, either in the drinking water (0-2 %) or by mixing it with the food (0 1 %). Radioactive orthophosphate (carrier-free 32p, 100-300 luc) was given by injection into the muscle of the hind limb. Foetuses were removed by Caesarean section after anaesthetizing the mother with intravenous pentobarbitone (40 mg/kg i.v.). In some experiments the whole litter was removed on the appropriate day. In others, two or three foetuses were taken at the same time and the uterus and abdominal * British Council Scholar, 1959-60.

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