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At least 343 records · Page 19Linked to original sources
PubMed2001

The avian tail reduces body parasite drag by controlling flow separation and vortex shedding.

The aerodynamic effect of the furled avian tail on the parasite drag of a bird's body was investigated on mounted, frozen European starling Sturnus vulgaris in a wind tunnel at flight speeds between 6 and 14 m s(-1). Removal of tail rectrices and dorsal and ventral covert feathers at the base of the tail increased the total parasite drag of the body and tail by between 25 and 55%. Flow visualization and measurements of dynamic pressure in the tail boundary layer showed that in the intact bird a separation bubble forms on the ventral side of the body, and reattaches to the ventral side of the tail. This bubble is a consequence of the morphology of the body, with a rapid contraction posterior to the pelvis and hind legs. The tail and the covert feathers at its base act as a combined splitter plate and wedge to control vortex shedding and body wake development, and thereby are important to minimize drag. This hitherto unsuspected mechanism is central to understanding the morphology of the avian body, and may have had a significant influence on the evolution of avian tail morphology by pre-adapting the tail for radiation and specialization as an aerodynamic lifting structure and as an organ of communication in sexual selection.

Animals↗
PubMed1985

Isolation and characterization of the bacteriophage T4 tail-associated lysozyme.

Direct evidence has been obtained that the tail-associated lysozyme of bacteriophage T4 (tail-lysozyme) is gp5, which is a protein component of the hub of the baseplate. Tails were treated with 3 M guanidine hydrochloride containing 1% Triton X-100, and the tail-lysozyme was separated from other tail components by preparative isoelectric focusing electrophoresis as a peak with a pI of 8.4. The molecular weight as determined from sodium dodecyl sulfate electrophoresis was 42,000. The tail-lysozyme was unambiguously identified as gp5 when the position of the lysozyme was compared with that of gp5 of tube-baseplates from 5ts1/23amH11/eL1ainfected Escherichia coli cells by two-dimensional gel electrophoresis. The tail-lysozyme has N-acetylmuramidase activity and the same substrate specificity as gene e lysozyme; the optimum pH is around 5.8, about 1 pH unit lower than for the e lysozyme. We assume that the tail-lysozyme plays an essential role in locally digesting the peptidoglycan layer to let the tube penetrate into the periplasmic space. The tail-lysozyme is presumably also responsible for "lysis from without."

Hydrogen-Ion Concentration↗
PubMed1982

Evidence for on-off control of heat dissipation from the tail of the rat.

Anterior hypothalamic temperature, tail vasoactivity, and tail heat loss were observed in unanaesthetised rats resting at an ambient temperature that was varied between 25 and 35 degrees C between experiments, but was held constant within an experiment. Vasodilation and vasoconstriction at the tail were qualitatively detectable by the appearance and disappearance of temperature differences between the tail surface overlying the ventral arterial supply, and the lateral venous drainage. Vasodilation detected this way was an abrupt singular event (being either on or off), and preceded subsequent exponential changes in tail surface temperature and heat loss. Within the ambient temperature range of 29--33 degrees C, the following sequence occurred in a 20-min cycle, despite the noncycling constant environmental and metabolic heat loads: tail vasodilation - 0.2 to 0.4 degrees C fall in hypothalamic temperature - tail vasoconstriction - 0.2 to 0.4 degrees C rise in hypothalamic temperature. This behaviour, consistent with the limit-cyclic behaviour of some nonlinear controllers, as well as the abrupt two-state nature of vasoactivity at the rat tail, provides evidence that the mechanism can be described by an on-off control model. In addition, angiography suggests that vasoconstriction rather than countercurrent heat exchange provides the major barrier to core to tail heat flow during the "off" phase.

Animals↗
PubMed1996

Differential responses of Aplysia siphon motor neurons and interneurons to tail and mantle stimuli: implications for behavioral response specificity.

1. Tail shock and mantle shock elicit different forms of siphon responses in Aplysia (flaring and backward bending vs. constriction and forward bending, respectively). Moreover, training with these two unconditioned stimuli (USs) in US-alone or classical conditioning paradigms differentially modifies the direction of the response to a siphon tap subsequently presented. As a first step toward addressing neural mechanisms underlying this response specificity, we systematically mapped the central siphon withdrawal circuit to determine which motor neurons and interneurons are differentially engaged by, and potentially modified by, tail and mantle USs. We utilized semi-intact preparations consisting of the intact mantle organs (including the gill and siphon), the tail, and the abdominal and circumesophageal ganglia. USs were delivered either cutaneously through silver wires implanted in the tail and mantle or via suction electrodes to the tail and branchial nerves. 2. We found that one class of central siphon motor neurons, the LFSB cells, was preferentially activated by tail USs, whereas other siphon motor neurons, the LBs cells and RDs cells, were preferentially activated by mantle USs. These motor neurons thus appear to be the final common path for the differential siphon movements to these USs. In addition, because activation of these cells can elicit neuromuscular facilitation and thereby enhance siphon movements, this differential activation may contribute to behavioral response specificity by imposing a specific response bias. 3. L29 interneurons, which both mediate and modulate the siphon withdrawal response, responded preferentially and exhibited synaptic facilitation selectively in response to tail shock USs. In contrast, L34 and the interneuron II network did not show differential activation. Facilitation at L29-LFSB connections following training with tail shock may contribute to tail-directed siphon responses to siphon tap and may thus be an additional mechanism contributing to behavioral response specificity. Possibly, facilitation at other L29 connections could also enhance its modulatory capabilities. 4. The generation of specific response topographies thus appears to involve the coordinate regulation of diverse neuronal elements and multiple mechanisms, which may contribute to different aspects of learning.

Animals↗
PubMed2005

Wnt/beta-catenin regulation of the Sp1-related transcription factor sp5l promotes tail development in zebrafish.

Tail formation in vertebrates involves the specification of a population of multipotent precursors, the tailbud, which will give rise to all of the posterior structures of the embryo. Wnts are signaling proteins that are candidates for promoting tail outgrowth in zebrafish, although which Wnts are involved, what genes they regulate, and whether Wnts are required for initiation or maintenance steps in tail formation has not been resolved. We show here that both wnt3a and wnt8 are expressed in the zebrafish tailbud and that simultaneous inhibition of both wnt3a and wnt8 using morpholino oligonucleotides can completely block tail formation. In embryos injected with wnt3a and wnt8 morpholinos, expression of genes in undifferentiated presomitic mesoderm is initiated, but not maintained. To identify genes that might function downstream of Wnts in tail formation, a DNA microarray screen was conducted, revealing that sp5l, a member of the Sp1 family of zinc-finger transcription factors, is activated by Wnt signaling. Moreover, we show that sp5l expression in the developing tail is dependent on both wnt3a and wnt8 function. Supporting a role for sp5l in tail formation, we find that inhibition of sp5l strongly enhances the effects of wnt3a inhibition, and overexpression of sp5l RNA is able to completely restore normal tail development in wnt3a morphants. These data place sp5l downstream of wnt3a and wnt8 in a Wnt/beta-catenin signaling pathway that controls tail development in zebrafish.

Animals↗
PubMed1998

Molecular identification of spadetail: regulation of zebrafish trunk and tail mesoderm formation by T-box genes.

Inhibition of fibroblast growth factor (FGF) signaling prevents trunk and tail formation in Xenopus and zebrafish embryos. While the T-box transcription factor Brachyury (called No Tail in zebrafish) is a key mediator of FGF signaling in the notochord and tail, the pathways activated by FGF in non-notochordal trunk mesoderm have been uncertain. Previous studies have shown that the spadetail gene is required for non-notochordal trunk mesoderm formation; spadetail mutant embryos have major trunk mesoderm deficiencies, but relatively normal tail and notochord development. We demonstrate here that spadetail encodes a T-box transcription factor with homologues in Xenopus and chick. Spadetail is likely to be a key mediator of FGF signaling in trunk non-notochordal mesoderm, since spadetail expression is regulated by FGF signaling. Trunk and tail development are therefore dependent upon the complementary actions of two T-box genes, spadetail and no tail. We show that the regulatory hierarchy among spadetail, no tail and a third T-box gene, tbx6, are substantially different during trunk and tail mesoderm formation, and propose a genetic model that accounts for the regional phenotypes of spadetail and no tail mutants.

Amino Acid Sequence↗
PubMed2000

Fate and function of the ventral ectodermal ridge during mouse tail development.

In the mouse embryo, the body axis continues to develop after gastrulation as a tail forms at the posterior end of the embryo. Little is known about what controls outgrowth and patterning of the tail, but it has been speculated that the ventral ectodermal ridge (VER), a morphologically distinct ectoderm on the ventral surface near the tip of the tail, is a source of signals that regulate tail development (Grüneberg, H. (1956). Nature 177, 787-788). We tested this hypothesis by ablating all or part of the VER and assessing the effects of such ablations on the development of tail explants cultured in vitro. The data showed that the VER produces signals necessary for somitogenesis in the tail and that the cells that produce these signals are localized in the middle and posterior region of the VER. Dye labeling experiments revealed that cells from these regions move anteriorly within the VER and eventually exit it, thereby colonizing the ventral surface ectoderm anterior to the VER. In situ hybridization analysis showed that the genes encoding the signaling molecules FGF17 and BMP2 are specifically expressed in the VER. Assays for gene expression in VER-ablated and control tails were performed to identify targets of VER signaling. The data showed that the VER is required for expression of the gene encoding the BMP antagonist noggin in the tail ventral mesoderm, leading us to speculate that one of the major functions of the VER in tail development is to regulate BMP activity.

Animals↗
PubMed1983

Dissociation of intermolecular linkages of the sperm head and tail by primary amines, aldehydes, sulphydryl reagents and detergents.

Primary amines, pyridoxal and thiols induced separation of the mammalian sperm head and tail at specific sites across the head-tail junction. Primary amines and pyridoxal induced head detachment by allowing separation of the inner and outer nuclear envelope membranes adjacent to the tail basal plates. This detachment was prevented by prior reduction with sodium cyanoborohydride. The chemistry of amine-induced head separation and the similar action of pyridoxal indicate that the head and tail are joined by Schiff bases formed between proteins within the nuclear membranes. Head detachment with thiols occurred at two sites: across the connecting filaments linking the basal plate and the capitulum of the tail-neck complex and between the inner nuclear membrane and the nuclear chromatin. Mammalian epididymal spermatozoa exhibited species differences in susceptibility to head detachment induced by hydromechanical shear. The heads of mouse epididymal spermatozoa readily separated from the tails during vortexing whereas those from the vas deferens were resistant to shear. Head separation occurred at the same site as induced by primary amines. Rabbit spermatozoa from all parts of the epididymis were resistant to mechanical shear. Species differences in the mechanical stability of the head-tail junction suggest that the intermolecular Schiff bases linking the head and tail can be formed before or during sperm transport in the epididymis and that their formation probably occurs after the appearance of the periodic structures which bridge the inner and outer membranes of the nucleus in the region of the tail basal plate.

Aldehydes↗
PubMed2003

Length of docked tail and the incidence of rectal prolapse in lambs.

A multistate cooperative study was conducted to study the current issue of tail length in docked lambs and its relationship to incidence of rectal prolapse. A total of 1,227 lambs at six locations were randomly allocated to two or three tail dock treatments: 1) short--tail was removed as close to the body as possible, 2) medium--tail was removed at a location midway between the attachment of the tail to the body and the attachment of the caudal folds to the tail, and 3) long--tail was removed at the attachment of the caudal folds to the tail. Short-docked lambs had a greater (P < 0.05) incidence of rectal prolapse (7.8%) than lambs with a medium (4.0%) or a long (1.8%) dock. Female lambs had a higher (P < 0.05) incidence of rectal prolapse than male lambs. At two stations, lambs were finished either in a feedlot on a high-concentrate diet or on pasture with no grain supplementation. At one station, with a very low incidence of rectal prolapse, there was no difference in incidence between lambs finished in the feedlot or on pasture; however, at the station with a relatively high incidence of rectal prolapse, lambs in the feedlot had a higher (P < 0.05) incidence than lambs on pasture. The half-sib estimate of heritability for the incidence of rectal prolapse was low (0.14). The results of this study strongly implicate short dock length as a cause of rectal prolapse in lambs finished on high-concentrate diets. Furthermore, the results of this study and the only other study known conducted on this issue strongly suggest that docking lambs at the site of the attachment of the caudal folds to the tail will result in a negligible incidence of rectal prolapse.

Animal Husbandry↗
PubMed2006

Complement-mediated tail degradation of Neodiplostomum seoulense cercariae.

The furcocercus cercariae of Neodiplostomum seoulense (Digenea: Neodiplostomidae) penetrate the skins of tadpoles and shed their tails. The speculated mechanism of this tail loss was physical efforts required to produce a vigorous zigzag motion during skin penetration; no other mechanism has been proposed. We examined the relationship between the host serum and cercarial tail loss. Cercariae of N. seoulense were collected from experimentally infected Segmentina hemisphaerula, and lots of 300 cercariae were cultured in medium 199 contained several types of sera. Cercarial tail degradation was induced in all media, but all the cercariae cultured except those cultured in media containing fetal bovine serum (FBS) died within 48 hr. After 72 hr cultivation in media containing FBS, cercarial tail degradation was induced in 67.0%; in continuous cultivation 13.3% of larvae survived for 7 days. Tail degradation did not occur in the absence of serum and when serum was heat inactivated at 56 degrees Celsius for 30 min. The addition of 20 mM ethylenediaminetetraacetic acid (EDTA) blocked cercarial tail degradation completely. Moreover, the addition of 20 mM MgCl2 restored tail degradation blocked by EDTA. These results suggest that the alternative complement pathway is related with the N. seoulense cercarial tail degradation induced by serum.

Animals↗
PubMed2000

Electromyographic and kinematic studies of tail movements during falling in cats.

When falling from an inverted position, EMG activities of tail muscles (the m. extensor caudae lateralis, m. abductor caudae externus, m. flexor caudae longus) and tail movements were recorded in 7 long-tailed adult cats. After being released from an elevated position, cat rotates the tail in a reverse direction to rotation of other parts of the cat's body then lands on four legs. Rotation of the tail was started by EMG activities of the tail muscles on one side. Both synchronized and alternating groups of discharge occur between its left and right side, while extensor and flexor movements and displacements of its tail appear in the air. After transection of ventral roots from the coccygeal spinal segments innervating tail muscles, cats often fail to land on four legs. These facts suggest that that tail movements control body balance in the air when falling from an inverted position.

Animals↗
PubMed1982

[Tail-biting in pigs. Causes, effects and prevention].

Although much is known of the causes and prevention of tail-biting, this continues to be a common vice in pigs. The animals seek diversion by chewing on the tails of their fellows as they feel uncomfortable. This may result in inflammation of the tail. Prevention should be directed towards improvement of the conditions which cause the animal to feel uncomfortable. As this will often not be possible or only in part, efforts are made to prevent tail-biting by docking the tails. When tail-docking is performed according to the rule in one- to three-day-old animals, tail-biting obviously will no longer be possible. However, this does not mean removing the causes of tail-biting. This procedure is therefore undesirable from the point of view of welfare of the animals. Inflammation of the tail may result in metastasis to the spinal column and/or lungs. This is frequently associated with bacteraemia. Moreover, the resulting abscess formation will be highly objectionable from the point of view of hygiene.

Animal Feed↗
PubMed1994

Identification and characterization of pleural neurons that inhibit tail sensory neurons and motor neurons in Aplysia: correlation with FMRFamide immunoreactivity.

Neurons on the rostral edge of the ventral surface of the right pleural ganglion were identified as elements of the circuit mediating the defensive tail withdrawal reflex of Aplysia. These neurons produced IPSPs in tail sensory neurons and were classified into two groups, RPI4 and RPI5, according to their affinity for an antibody directed against FMRFamide. RPI4 was not FMRFamide immunoreactive, and RPI5 was. RPI4 and RPI5 were found to have different electrophysiological profiles. The summated IPSPs in sensory neurons produced by RPI4 developed more rapidly and had a shorter duration than those produced by RPI5. In addition, RPI4 produced IPSPs in the tail motor neurons, whereas RPI5 did not. Both RPI4 and RPI5 received excitatory synaptic inputs from stimulation of the pleural-abdominal connective as well as peripheral nerves P8 and P9, which innervate the tail and posterior part of the animal's body. These inputs were sufficient to elicit spikes. In RPI4, the excitatory synaptic inputs were followed by short and transient hyperpolarization, whereas in RPI5, the excitatory synaptic inputs were followed by slow and long-lasting hyperpolarization. Excitatory inputs elicited in RPI4 by stimulation of peripheral nerves appeared to be mediated, at least in part, by activation of tail sensory neurons. Intracellular stimulation of sensory neurons produced EPSPs in RPI4 that appeared to be monosynaptic. These results suggest that inhibitory interneurons underlying the circuit of the tail withdrawal reflex may play roles in mediating or modulating neuronal responses to tail stimulation. By inhibiting tail sensory and motor neurons, these interneurons may reduce the effectiveness of an animal's response to stimulation of the tail.

Animals↗
PubMed1997

Heterologous desensitization of the rat tail artery contraction and inositol phosphate accumulation after in vitro exposure to phenylephrine is mediated by decreased levels of Galphaq and Galphai.

Desensitization of alpha-1 adrenoceptor (alpha1AR)-mediated responses in aortic smooth muscle after exposure to catecholamines or alpha1AR agonists has been widely demonstrated. To determine whether exposure to an alpha1AR agonist results in desensitization of alpha1AR-mediated responses in a resistance artery, rat tail artery rings were exposed to 7.5 or 75 microM phenylephrine (PE) for 22 hr in vitro. Norepinephrine-stimulated contraction was significantly reduced in PE-exposed tail artery rings. Contractions mediated by the alpha2AR agonists, clonidine and UK 14,304, and by serotonin were also reduced in PE-treated tail artery rings. However, the contractile responses to KCl and ionomycin remained unchanged. Norepinephrine-, PE-, endothelin- and serotonin-stimulated inositol phosphate accumulations were reduced in PE-exposed tail artery rings, whereas KCl- and ionomycin-stimulated inositol phosphate accumulation remained unchanged. The density of membrane alpha1ARs, measured by specific [125I]2-([beta-(4-hydroxyphenyl)ethyl]aminomethyl)-1-etralone binding was not changed in PE-desensitized tail arteries. Further studies were performed to examine if alterations in receptor/G protein interaction accompanies arterial desensitization. In these studies receptor-stimulated increases in [35S]GTPgammaS binding to G proteins was assessed in membranes obtained from vehicle (control) and PE-treated tail arteries. In control membranes alpha1AR stimulation increased [35S]GTPgammaS binding to Galphaq and Galphai proteins, whereas the alpha2AR agonist UK14,304 activated [35S]GTPgammaS binding to Galphai exclusively. Both PE- and UK14, 304-induced responses were reduced in membranes from tail arteries that were exposed to either 7.5 or 75 microM PE for 22 hr. Western blot analyses of G protein alpha and beta subunits demonstrated that Galphaq and Galphai protein levels were decreased in PE-exposed tail artery membranes. These data show that the reduced transmembrane signaling for the alpha1AR in tail artery after in vitro PE exposure is associated with decreases in Galphaq and Galphai protein levels. The reduction in these Galpha proteins also appears to mediate the loss of function of alpha2AR and perhaps of other G protein-coupled receptors.

Adrenergic alpha-Agonists↗
PubMed1998

Uneven distribution of desmosterol and docosahexaenoic acid in the heads and tails of monkey sperm.

Previously we demonstrated high concentrations of desmosterol and docosahexaenoic acid (DHA, 22:6 n-3) in monkey testes and sperm. Desmosterol, a cholesterol precursor, is not present elsewhere in the body. High concentrations of DHA are found elsewhere only in the retina and brain. To examine the distribution of these compounds in the heads and tails of sperm, we separated them and determined their sterol, fatty acid, and phospholipid molecular species composition. Desmosterol predominated in tails (134.4 vs. 1.7 microg/10(9) cells in heads). The cholesterol content was also greater in the tails (66.2 vs. 30.3 microg/10(9) cells in heads). Sperm tails had more polyunsaturated fatty acids than the heads (34.1 vs. 12.1% of total fatty acids) which resulted mainly from the higher contents of DHA (19.6 vs. 1.1%) and arachidonic acid (20:4 n-6) (6.4 vs. 1.6%) in the tails. These differences in fatty acid composition occurred mainly in phospholipids: phosphatidyl choline and phosphatidyl ethanolamine for n-3 fatty acids and phosphatidyl serine and cardiolipin for n-6 fatty acids. Fifteen phospholipid molecular species were identified. Sperm tails had more molecular species containing unsaturated fatty acids than the heads. Our results reveal the large differences in membrane lipid composition between the heads and tails of sperm. Most (99%) of the desmosterol and DHA in sperm is located in the tail. These differences may be responsible for the different functions of these two components of sperm. The large number of double bonds in DHA, six, and in desmosterol, two, may contribute to the membrane fluidity necessary for the motility of the sperm tails.

Animals↗
PubMed1997

Possible roles for Wnt genes in growth and axial patterning during regeneration of the tail in urodele amphibians.

Urodele amphibians are nearly the only adult vertebrates able to regenerate their missing or amputated tail. An interesting aspect of this biological model lies in the ability of regenerates to differentiate the spinal cord (SC), the vertebral cartilage, and muscles. The main questions addressed in this study concern the possible roles of Wnt genes in these regenerative processes. We have previously reported the expression pattern of a Pleurodeles Waltl wnt-10a gene (Pwnt-10a) in tail blastema (Caubit et al. [1997] Dev. Dyn. 208:139-148). We report here the cloning and tissue distribution of three additional Wnt genes (Pwnt-5a, Pwnt-5b, and Pwnt-7a) in adult and regenerating tail tissues and in the central nervous system (CNS) of adult newt. In adult and regenerating tails, Pwnt-5a and Pwnt-5b transcripts exhibit a graded distribution along the antero-posterior (A-P) axis, the maximal accumulation of these transcripts being detected in the mesenchyme within the subectodermal apical region of the normal tail and blastema. In contrast to Pwnt-5a and Pwnt-5b, Pwnt-7a is expressed in adult normal tail skin and in the epidermis of the regenerating tail. In the adult CNS, Pwnt-5a, Pwnt-5b, Pwnt-7a, and Pwnt-10a genes are expressed in sharp overlapping but not identical domains along the A-P axis. The sustained expression of Wnt genes in the adult newt and the spatial distribution of transcripts in adult and regenerating tail tissues suggest roles of these genes in continuous growth capacities in the urodeles and may explain the ability for CNS and tail regeneration.

Amino Acid Sequence↗
PubMed1994

The influenza virus hemagglutinin cytoplasmic tail is not essential for virus assembly or infectivity.

The influenza A virus hemagglutinin (HA) glycoprotein contains a cytoplasmic tail which consists of 10-11 amino acids, of which five residues re conserved in all subtypes of influenza A virus. As the cytoplasmic tail is not needed for intracellular transport to the plasma membrane, it has become virtually dogma that the role of the cytoplasmic tail is in forming protein-protein interactions necessary for creating an infectious budding virus. To investigate the role of the HA cytoplasmic tail in virus replication, reverse genetics was used to obtain an influenza virus that lacked an HA cytoplasmic tail. The rescued virus contained the HA of subtype A/Udorn/72 in a helper virus (subtype A/WSN/33) background. Biochemical analysis indicated that only the introduced tail- HA was incorporated into virions and these particles lacked a detectable fragment of the helper virus HA. The tail- HA rescued virus assembled and replicated almost as efficiently as virions containing wild-type HA, suggesting that the cytoplasmic tail is not essential for the virus assembly process. Nonetheless, a revertant virus was isolated, suggesting that possession of a cytoplasmic tail does confer an advantage.

Amino Acid Sequence↗
PubMed1982

Structural characteristics of the short-tail fibers of T4 bacteriophage.

The characteristics of pure preparations of short-tail fibers of bacteriophage T4 have been studied in the optical and electron microscope. Three main structures were observed: 1) spheres of 8.1 nm diameter; 2) fibers 43 nm long and 3.8 nm thick; and 3) fibers 54 nm long and 3.2 nm thick. Both types of fibers exhibited a regular beaded appearance. The 43-nm fibers were the most abundant structure. During the process of purification of the short-tail fibers, the formation of aggregates was observed each time the material containing the short-tail fibers was dialyzed against saline solutions. These aggregates became increasingly fibrous (as observed in the optical microscope) as the material used was increasingly enriched in short-tail fibers. Finally, most of the aggregates were of the fibrous type when they were formed from a purified preparation of short-tail fibers. In the electron microscope, it was found that the filamentous aggregates were organized in well-defined bundles. The amino acid composition of the highly purified short-tail fibers was also determined. Among the known fibrous proteins, the ones that most resemble the amino acid composition of the short-tail fibers are actin and fibrinogen. These observations are discussed in relation to the T4 short-tail fiber structure and their localization on the hexagonal baseplate of the T4 tail structure.

Amino Acids↗